Update:

Seems to be related to me being on an Irish server on my VPN. Spoke with the admin, they're blocking VPN's due to bad actors in the past.

It says "Join lemmus.org", but clicking on it returns an error - either the instance doesn't exist anymore or it's temporarily unavailable.

Either way, it's not great. I'm on this reddit thread and people are saying how the whole "choosing a server" is a difficult barrier and was going to show them the join-lemmy site, but... yeah.

How does the join-lemmy.org site determine which instance to send users to?