Pretty sure they’re installed by default. At least in ubuntu.

https://ubuntu.com/server/docs/nvidia-drivers-installation

Why not use proxmox? Then passthrough the gpu to distro of your choice? I have 2x headless ubuntu set ups with gpu’s passed through no problem. One for plex/jellyfin, one for cameras

Authentik will manage users/groups provide an ldap server and do all single factor and multi factor auth. Cooptonian has great guides on youtube.