Which ones? Most of them simply white list pubkeys. There isn't anything special in amethyst code to work with them. Just make sure you are using the same pubkey you paid them on.
Discussion
I am, only ever used this pub key
going to have to investigate this further
after manually clicking them in the "Relay" tab, I can publish to them
very weird, as if the client only learned of that relay after I forced it to fetch something about it?
Yep, you have to press post to create your nostr contact list in that relay. Otherwise, everytime the app restarts, it won't find a contact list with that relay in it.