DRM can work on Linux, it's just developers choose to not enabled support, and in some cases (Epic Games) actively update games so it won't work with Linux.
But yes - the problem is Epic doesn't target Linux with it, not that it would be infeasible for Epic to support playing Fortnite on Linux if they changed their minds.
There is probably more nuance behind that decision than I’m giving them credit for, but from a technical standpoint it’s just a checkbox.
[1] https://dev.epicgames.com/docs/game-services/anti-cheat/usin...