There is also Kaldi, but it’s not on F-Droid though.

https://k2-fsa.github.io/sherpa/onnx/tts/apk-engine.html

Have you tried the fixes in the comments of this page?

https://aur.archlinux.org/packages/gzdoom

I find the comments in the AUR package page the best source of information to debug AUR issues.

Anyway, if you don’t want to use exactly that AUR package, there are multiple ways to install gzdoom witch some may be easier to install. You many different packages come up when you search gzdoom.

And what comes to other options, for Steam users there is luxtorpeda that integrates with Steam. Lutris users have their gzdoom runner. For the rest there is flatpak version available.