I agree with the sentiment but Kodi isn't really a direct replacement for a plex server, it's a client replacement. You want Jellyfin or at least a mysql backend for Kodi to get the shared watched status and such.

I use opentofu and the bgp proxmox terraform provider to automate this. You don't even need to set up templates as you can download and use cloud images for the various distributions with terraform and use them to initialise the boot disk on the VM. You can define your users in the terraform and it will use cloud init to provision them including specifying uids and ssh keys.

If the app runs correctly in Wine you might be able to rig something together with that.

Another thumbs up here for Kodi. It's emulation capabilities aren't as mature as retroarch but it's much more couch friendly in my opinion. Still not quite the same as Jellyfin handling all the meta data though and sharing state.