I don't know about minefields but the GAU-8/A would do horrible things to Russian soldiers in the trenches plus it would be a good way to obliterate ammunition dumps, other storage sites, SAM sites and artillery (Both tube and rocket).
Absolutely horrible, would you volunteer to be in that cockpit? Brrrrrrrrrt, Russians running.
There are some better and some worse ideas on how to kill Ukrainian pilots; this one belongs to one of the too obvious ones.
Of course they'e likely to be shooting back but the A-10Cs (And likely AH-64 Apaches too) will be firing from a distance and these speedboat attacks appear generally happen at night so it would be a bit hard for the gunners to see them.
This is average "manpad"
on a modern Iranian speedboat.
It's somewhat telling I have to bring the picture full month since Ayatollah was killed. Though with gau-8 dreams on ukrainian front, sort of matches tbh.
They're still vulnerable due to the very same failure of Iranian GBADs (don't think this force is terribly survivable without extended ground umbrella), but direct gun runs(rockets included) aren't the idea you're looking for.
... it's called the threat environment has changed. When everyone and their brother has a MANPAD and (semi-competent at worst) IADS have been showing to tell aircraft where to stuff it, the A-10 becomes dead weight.
Ukrainian aircraft aren't famous for being able to operate high and fast near the frontline, though. Low and slow (at a tactical stand off) is far more doable v suppressed GBAD that still can hit things. Maneuver competition v effective missile in thinner air usually ends up with missile winning more often than not.
It's reasonable to justify it with 'high, fast, and stealth'(or at least EW) being proven over Iran. But the problem with Iranian systems is they can't bring down literally anything beyond MALE. High, low, fast, slow, stealth, no stealth, ew, no ew.