I've never used proxmox, but I've heard good things. Personally (and this is a bit crazy) the best bar none interface for containers I've used is the OpenMediaVault compose plugin - it's a NAS distro but I literally ran it on all my servers for years because of the UI

TrueNAS is also a NAS distribution and it has pretty good support for containers and VMs, so I’m not that surprised. They generally expect to be individual all-in-one type of servers.