The Mac gaming market is miniscule, and requires special special care (different arch and APIs) . It's highly unlikely many game developers will choose to spend that time and money.
Yeah it's takes some effort. But Source 2 supports it (DotA 2), Fortnite can be built efficiently so Unity can do it. That's 2 major engines available. Not to mention all the iOS games library that's actually able to run on the M1 pending the release configurations from each dev.
Fortnite is built on the Epic Games created Unreal Engine, not Unity.
Oh yeah Unreal. That's still a major game engine though. And Unity does support exporting for Apple Silicon/M1