I have run into the firewall problems before. Even seen them that block authentication but -if already connected to the tailnet before joining the WiFi in question - will continue to pass data. OpenVPN would not connect and couldn’t handle the IP address switch.

At worst, I turn on phone hotspot, authenticate, then switch back to WiFi. A purely serendipitous discovery on my part, but a very welcome one.

Interesting, maybe they block the orchestration servers of Tailscale, but not the actual data plane (which is almost always P2P, i.e., it usually does not involve Tailscale servers/IPs at all)?

I'm sure they do, but the question is, why did OpenVPN fail? It's pure P2P. I've got a dynamic DNS through afraid.org, and that resolves on that network, so it's not just DNS-level blocking. I effectively have a static IP anyway; there's no CGNAT going on, so I've discovered that I misconfigured my DDNS once or twice only when afraid.org emailed to tell me that I hadn't updated in X months.

Were you using the semi-well-known port (1194)? Otherwise, maybe it's just more fingerprint-able, or whatever DPI the firewall uses hasn't caught up to Wireguard yet?