I have a group of people (an alumni group) that I would like to try Nostr with in a more private mode. We can run a private relay, what would be the best user interfaces for that? Meaning I can easily choose on post screen where I'm posting and I can have a tab in the app with global feed from one relay.

I don't want to limit people to that relay though, it could be a great way to onboard people to general Nostr, so I would like them to be able to follow people on public relays too.

What would be the best way to do this? I don't want any hacks like "use one app and delete all relays and add the private one and use another app for normal nostr".