I think the “recipe app” is a great example, specifically because it’s not “yet another microblogging Twitter clone” that seems to permeate the Fediverse.
If we are serious about interoperability, it means that people on my music sharing site should be able to collaborate at some level with people on your recipe app. Each app should participate in the global ecosystem, instead of making siloed, incompatible networks surrounding each applications (with FunkWhale’s as an example of this)
Obviously, every app can’t be everything to everyone (which is kinda how AP currently operates) so what are the commonalities? What is the “Lowest Common Denominator” of the Fediverse?
I’ll propose that it’s: 1) identity, and 2) notifications. My username should be the master key that opens every door on the Fediverse, and allows me to subscribe to events in a myriad of other services. In this model, my Mastodon account doesn’t need to know how music (or recipes) are handled on remote servers, but I can get access to them, and seamlessly connect to those other specialized services when I want to.