@Surf Just to follow up on this a little, I was trying on Android and it was saying it couldn't find a mastodon instance at death.id.au (my friendica instance) and the Connect button was greyed out.

I tried again on the web, and while the button was still greyed out, I pressed enter and it submitted anyway and actually redirected to the OAuth page for my instance! However, after authorising, it just took me back to the surf.social home page and the account was not connected.