Ok, I think I understand what you're saying now. I fixed the perms.
LXc:
# ls -nal /dev/net/tun
crw-rw-rw- 1 0 0 10, 200 Jan 7 19:18 /dev/net/tun
PVE:
# ls -nal /dev/net/tun
crw-rw-rw- 1 100000 100000 10, 200 Jan 7 19:18 /dev/net/tun
Still having the same issue.
# mullvad connect...