I recently needed to set up Tailscale in an AlmaLinux 9 LXC container running on my Proxmox 8.2 server. Following the official instructions from Tailscale’s RHEL 9 guide and even trying their Linux install script, I ran into some issues. The main problem turned out to be missing TUN device support in the LXC container.

I had to edit the LXC container configuration on the Proxmox host:

nano /etc/pve/lxc/<container-id>.conf

And add these lines:

lxc.cgroup2.devices.allow: c 10:200 rwm

lxc.mount.entry: /dev/net/tun dev/net/tun none bind,create=file

Here is the article in case is useful for someone else.