I was thinking about changing my server’s OS (currently using Ubuntu server)
Which would be the best in the case of only using docker and ZFS?
I thought that Debian would be more debloated and efficient but I need a Web UI and from what I have seen TrueNAS is very complete and is not absurdly slow, let me know your thoughts!
Truenas scale is Debian, if you just use it remotely it may be a good bet. If you may use the server as workstation (e.g. desktop) then you better use Debian itself (or both, as VMs under Proxmox). Managing ZFS is super easy, just create a couple of volumes with small and big blocksize, in either cockpit or whatever web ui. You may also switch OS (e.g. disaster or play around), and recover these effortlessly with
zfs import
command from CLI. Good luck!