Metallica works, Slipknot doesn't, Iron Maiden does, Nirvana doesn't.

Aperture Science works, so does Black Mesa (the proposed opponent, hehe), Cyberdyne Systems doesn't, Vault-Tec does, Weyland-Yutani also works.

Studio Ghibli doesn't work, Toei Animation does, so does Production I.G. and KyoAni.

Akagi works, JoJo doesn't but JoJo Bizarre Adventure does (so does Joseph Joestar, and it knows Dio Brando is the opponent), Uzumaki does not, BLAME! is accepted but not recognized (a shame), 20th Century Boys is not accepted.

Soviet Union works, Russia does not, neither do most countries. US States are accepted (California's opponent is Florida), so do many cities, with exceptions of Mexico City/Ciudad de Mexico, Pyongyang and Tehran.

Voyager-1 works, Apollo 13 doesn't (for any mission numbers), plain Apollo does (but it's not the space mission), Soyuz does, SpaceX Starship does not.

Vim works, so does Emacs, so does Visual Studio. (I've tried that just to see the proposed opponents)

Dota 2, S.T.A.L.K.E.R., Mass Effect, Half-Life, Deus Ex, Arma 3, BioShock, Elden Ring all work, even Wolfenstein does. Disco Elysium is accepted but produce something unrelated (a shame, again). Can't find a video game that won't be accepted.

Funnily, US Government worked partially for me, failing to produce a single piece.

I generated a classic chess set based on Nowruz and it generated Hanukkah as the opponent x_x