Noted for me adding tuneling at proxmox lxc.
Open proxmox host shell and open /etc/pve/lxcnumber/lxc.conf (/etc/pve/100/100.conf) and then add this
lxc.cgroup2.devices.allow: c 10:200 rwm lxc.mount.entry: /dev/net dev/net none bind,create=dir and then
chown 100000:100000 /dev/net/tun
after that reboot the container and voila success if problem still occure change dns setting add 1.1.1.1 to the dns server
Thats it, its works for me
Happy coding and Salam ngoprek