Now you are exposed to every security bug in Tailscale's client, DERP relays, and coordination plane, plus you have added a trust dependency on infrastructure you do not control. The attack surface did not shrink, it shifted.
I run the tailscale client in it's own LXC on Proxmox. Which connects to nginx proxy manager also in it's own LXC, which then connects to Nextcloud configured with all the normal features (Passkeys, HTTPS, etc). The Nextcloud VM uses full disk encryption as well.
Any one of those components might be exploitable, but to get my data you'd have to exploit all of them.
You do not need to exploit each layer because you traverse them. Tailnet access (compromised device, account, Tailscale itself) gets you to nginx. Then you only need to exploit Nextcloud.
LXC isolation protects Proxmox from container escapes, not services from each other over the network. Full disk encryption protects against physical theft, not network attacks while running.
And if Nextcloud has passkeys, HTTPS, and proper auth, what is Tailscale adding exactly? What is the point of this setup over the alternative? What threat does this stop that "hardened Nextcloud, exposed directly" does not? It is complexity theater. Looks like defense in depth, but the "layers" are network hops, not security boundaries.
And, Proxmox makes it worse in this case as most people won't know or understand that proxmox's netoworking is fundamentally wrong: its configured with consistent interface naming set the wrong way.
