The easiest way to avoid detection is to not look like a target. Depending on the sphere of battle this manifests differently.
This is increasingly difficult for ground armies when sensors get better and even five or six guys with a couple machine guns between them look tempting for a long range artillery attack. Shells are cheap. Soldiers aren't. Armies are, glacially, evolving into hit squads and civilian-dressed special forces teams al a Delta Force and CIA SAD. Eventually, something as powerful as a single tank will be detected from orbit and destroyed almost immediately, much less a platoon or company of them, so there won't be a reason for the superpowers to have them, at least for their own-wars.
Genocidal Organ, despite the major plot conceit being based on Chomskian linguistics (which, honestly, is not that bad), is actually a pretty decent portrayal of what future soldiers might look like, barring some of the more loopy animesque bits ("so how about it, you ready to kill some children?" lmfao); then again, a soldier's moral injury leading to the sabotage of a national war effort are hardly new irl. The part of that sabotage being successful is the animesque bit I guess, but a universal grammar would really be the ultimate weapon etc. I digress...
For warships, submarines are the obvious conclusion. Surface ships will have their purpose for small wars, like Russia vs. Ukraine, but against other big countries the surface ship is not very useful from the start as it is too easily destroyed. Whether they will be useful at all or completely useless (i.e. do they go in after the destruction of airbases by cruise missile attack or do they get their home ports nuked and have nowhere to return to) is for the future to reveal. Much like how armies may retain token ground forces for purposes of parades (a couple hundred or dozen tanks is more than adequate to subdue a third world country like Afghanistan), navies may be primarily measured by their submarine forces but retain token surface fleets for more common but not particularly useful (at the upper end of the escalation ladder that is) jobs like showing the flag or participating in confidence exercises.
For aircraft, and spacecraft, the already decided on future is VLO stealth and subsonic attack aircraft. Going very slowly will all but eliminate the thermal signature, which can be detected from orbit by last generation space-based IR sensors, and perhaps something like piezoelectric skin can be used to further mask the thermal signature by resembling the Earth below the plane using a multi-band DAS as a source IR image. That would make aircraft broadly immune to passive detection from above, and when combined with radar stealth, will make them tough to sus out before they hit their targets.
The greatest future threat to attack aircraft, after all, isn't other aircraft, but rather orbital detection networks of LEO-based AMTI radars and thermal-infrared detection networks al a SBIRS-LO. Spacecraft will have immunity to attack based on either altitude (above LEO) or sheer number (cubesat swarms) and likely be fired routinely into orbit both to replenish stocks of swarms (cubesats decay quickly) and battlefield losses from kamikaze cubes. Radar/laser jammers and stuff will not be particularly important since they will be extremely visible (there's a giant emitter *right there*) so you'd just kill them with AARGMs or something.
At this point, this future includes only the PRC and America, as these are the only countries which can domestically support major development of new generation aerospace forces and space industrial development. I don't see any European country, including Russia, getting there in the coming decades. Europeans will certainly reduce the size of their armies but neither UK/France/Germany troika nor Russia are economically developed enough to have their own domestic orbital electric eyes, although of the two it is Russia that is best positioned to support their patron state. They will still leech off the US and PRC respectively as they are the imperial peripheries to their colonial clients.
Naturally the problem is finding the labor and workforce to actually accomplish the construction of new submarines, new generations of warplanes, and training new special forces commandos to attack enemy national leaders, in the demographically declining West. Perhaps the fit, young males of the obsolete land armies of the world can be recycled from being soldiers to being welders and factory laborers though. The PRC has plenty of these, simply by nature of being undeveloped, while the West has few and getting less, so it's likely the West is going to continue falling behind the PRC in gross output.
Africa, the only place that is still demographically growing, is shaping up to be a pretty good proxy force for competing colonial hegemonies. Stuff like Syria, Ukraine, and Libya, where Western troops never touched the ground outside of special operations forces, are the portent of the future. Mali is the exception here, and even that is more using Westerners as shock troops and advisors than anything (being comparable to pre-2022 Ukraine war), and it's likely that mass occupations like the latter half of Afghanistan and all of Iraq will never be performed again (by the West, that is) simply because there won't be enough young men to fill out the ranks. Instead of a million European and American troops (ODS), or even a quarter million (OIF), it will be an invasion spearheaded by the Saudi and UAE armies, with advisors from the US and France, and one US or French battalion for every dozen or two dozen Arab battalions. Maybe two thousand Westerner ground troops total, and a quarter million Arabs? That would be a decent peg for a very major ground war of the future.
In other words, not being detected is impossible in the future. People will know something is there. They will aggressively be searching for it, too. They might miss it if it falls outside their area of expectation (machine learning is especailly vulnerable to this, which is why I don't think it will be helpful in sussing out insurgents or anything), so being targeted is another thing entirely. Everything from ballistic missile RVs to infantrymen are simply going to have to resemble things that aren't targets to neutralize the threat of airpower and allow the offense to take primacy again. There have been shades of this in Kosovo, Serbia, Iraq, where "anti-simulation" (for lack of a better term, I'm borrowing this one from ABM) decoys successfully tied down UN airpower but was not sufficient to bring victory. That's simply because Milosevic feared his own death more than he feared capitulation. Most recently in Afghanistan, "not resembling a target" was a successful tactic used against the international occupation forces though, so it apparently requires a force which is both unyielding and has an unmolested enclave of friendly territory, ideally supported by a third party that plays both sides.
It will require throwing out a lot of norms of war at the end of the day, but most norms were established when Europe was ascendant as a global hegemony and not a imperial periphery between globally competing American and Asian civilizations, so it follows that with a change of civilizations there comes a change of international norms. Things like perfidy and not wearing uniforms will become SOP, although they already are for Western special operations troops, in order to avoid stuff like automatic machine guns or Gorgon Stare-type WFOV sensors, etc. Camp Bastion inflicted on the Chinese by an American merchant marine crew of disguised Navy SEALs could be effective, especially if it destroys a large crop of advanced aircraft or trained pilots, for instance.
Most of this boils down to the US and PRC civilizations being close to demographic collapse (something which Europe writ large, as well as Korea and Japan, are already in the throes of) and inevitable economic excesses that brings though. I suspect this is less a facet of technology itself and more a facet of the societies we live in, which encourage things like consumerist consumption over raising families, by making TVs cheap and children expensive, for reasons of supporting individualism over collectivism. It's not a particularly desirable place to be since the only way forward after this is eventually these tiny hit squads of commandos, and their super expensive airplanes, will be so expensive they will be defeated when four of maybe a dozen fighter pilots in the nation will get into a car accident, and a more youthful and virile enemy just overruns the nation literally without firing a shot.
Small armies aren't a particularly nice place to be, and I suppose if you had sufficiently big armies, you could easily absorb the losses from these mega satellite networks and smart bombs by simply charging ahead. Unfortunately, no one is producing 50-100,000 units of a main battle tank like the T-55 or M4 Sherman anymore. If they did, they would hardly be able to find enough men to crew a tenth of that number. Perhaps someone will eventually, and I suppose those people will inherit the Earth, but it won't be the technologically advanced societies which consider production runs of 100-200 tanks to be "large" lol.
tl;dr Long range detection can only be "obfuscated" by not drawing attention to yourself, at least until they can be destroyed. In the majority of cases, these detection methods cannot be destroyed, and we're getting to the point where two competing superpowers will be in control of indestructible reconnaissance platforms. Jamming attacks draw attention to yourself, so are pretty much right out. If you can make a jammer that draws attention to itself and is either cheap enough to be expendable or robust enough to survive counter attack, then you might have a utility for it, though. It would be so that actual troops can move while the enemy's electric fovea is focused on a single target.
The only means of evading destruction at that point is to not look like a target. Either hide under something constantly like a submarine does, resemble something you aren't like an airplane's thermoelectric skin copying the thermal background of the Earth or clouds below it, or don't gaggle together in a big group that draws attention like not having a motor rifle company assembly area where everyone just vibes waiting to be struck by a fire strike. The best methods of doing this are to build more submarines (with stealth shaping like the Astute and Astute replacement, to evade strategic SURTASS LFA, of course) and fewer aircraft carriers; build active thermal-infrared stealth alongside radar stealth into the designs of new generation stealth aircraft that will succeed F-22/F-35; and exist as a small group of lightly loaded soldiers used to foraging and existing in situ with indigenous people like the U.S. Special Forces.
All the pieces are there it's just a matter of putting them together. Given the latest generation of aircraft in the world have had a gestation period of about 40 years once traced back to ASTOVL of the 1980's, it's still very far in the future, though.
