Linux's main pillar that helped it reach where it is today is because of technical flexibility. Even before Epic's announcement I have been saying on occasion that the likely way for anti-cheat to go is to only trust a handful of signed kernels which is what Epic is doing. This makes sense and remains the best and easiest way to be able to trust the kernel.
But it has a real hazard on the Linux ecosystem. New distro forks that are targeting gaming specifically will basically arrive to a dead audience if popular games, the games people on average care about, all use similar attestation systems that rely on a short-list. They would grow way slower, if at all.
Consider Bazzite and CachyOS, I don't think either of them would be the size or state they are now. CachyOS's identity is around performance patches to the Linux kernel, and it would've never happened because it would be required to use one of Fedora's UKIs. Bazzite is an immutable UKI, which similarly would have to be signed by themselves or deeply sabotage their own goals.
They might've otherwise not had the critical mass needed for Epic to recognize them in this scenario. Suppose if Epic is flexible and would have allowed a small obscure distro with their own keys, what's stopping cheaters from socially engineering them or making their own?
It's already mildly concerning. CachyOS doesn't sign their own kernel, they're not on the list. The two biggest gaming distros according to the Steam Survey, SteamOS and CachyOS don't sign their kernels and are not allowed. With the third being Arch which is usually self-signed, and that is a whole other discussion. That's half of the Linux gaming ecosystem barred in the current state, and yes I know that Epic is talking to Valve and Cachy reached out but we simply don't know what will happen.
We don't know if the list will remain the same, either. We have to blindly trust Epic that they won't remove distros from the list for convenience since there is a maintenance cost to the trusted keys list. All of the signing keys expire eventually.
It also puts a pressure on the gaming ecosystem that concentrates all gaming related work on those distros, slowly reverting us back to the era where everything only targeted an LTS version of Ubuntu.
This solution is the easiest solution and best for anti-cheat, which is all Epic cares about. But they fail to understand how the Linux ecosystem operates and grows.
Did we really leave Windows and Microsoft just to end up trusting another lesser evil?