I had a similar issue too. Tailscale messed up my resolv.conf and I rebuilt it to get basic dns working.

What I would do is look for a basic dns tutorial for Ubuntu to ensure either the local or remote dns server is working. Before you do that verify the internet is working by pinging something like 1.1.1.1 or 8.8.8.8 just as a sanity test. If that works then DNS is the last thing to get going.

Came to same conclusion too