LinuxGSM is a way to easily install, run and manage game servers.
They can either be installed natively in Linux, or as Docker Containers
They have an easy to configure config file that's similar across all games, they have features to easily install, update, validate and manage servers, with support for a lot of games.
I've personally been using it for years to host person servers and it's relatively easy to manually set up a custom app or yaml file in TrueNAS, especially since it only needs you to mount one storage location [/data] and everything is easily accessible inside there.
to pick a game, you just select the version of the docker container.
For example: gameservermanagers/gameserver:csgo Will make a CS:GO server, but changing the tag to :cs2 will download and create a CS:2 server, etc...
Having a one click installer or an app with an easy configuration would make things incredibly simple for most users, and thanks to how they're configured it (might, I'm not a developer, pls don't shoot me) be easy to implement.
Important Links:
https://linuxgsm.com/
https://github.com/GameServerManagers
attached are the example compose and config files for a CSGO server.
docker-compose-csgo.yml _default.cfg