I don't use Tailscale myself, but it could potentially be as simple as using Tailscale to connect to the LXC guest, then accessing the PVE web UI via its usual IP and port (assuming you don't have any firewall restrictions in place).
Known issue that's being addressed currently. You can try an experimental kernel build if you're brave:
https://forum.proxmox.com/threads/slow-memory-leak-in-6-8-12-13-pve.168961/post-803023