If you’re on a recent proxmox setup that uses LXC containers you might be able to export those containers using lxc-snapshot or some other method and move them to the LXD node… May work just fine, may require other adjustments.
Personally the move was worth it. I’m not gonna lie, a ton of my most complex solutions are setup using cloud-init and Ansible so moving from one solution to another was mostly running those again and watch the machines get re-created.