@seperis Fedilab on Android does this. Individual servers, but it's still really nice. My server has it as an option, too but it's buggy AF. I suspect they'll fix it soon.
@War_Kittens Okay, so Federated timeline isn't grabbing All Servers (Instances), it's grabbing All People (Statuses) and then applying the blocks to filter out. While I can see some workarounds, to do select-in you'd probably need an entirely different call.
@War_Kittens Note: this is really not how I expected the structure to look. I don't even see a way to call a single server because it doesn't care about servers, only users.
@seperis If you go to say, mastodon.social, there's an option to look at that server's local feed. I suspect it just uses that.
@War_Kittens I'm searching the mastodon API to get an idea of how they structure the API calls. You can select-out (block) servers from the public timeline but there's nothing (so far) that allows you to select in.
On a guess, the default for the public feed is it grabs everything then applies filters to block people or servers (first the server's own blocks, then the individuals I assume). There isn't anything that allows select-in on a server level.