I feel like there’s still a pretty big gap in the drawing / art space. I want something that works like the furry art sites all work, which means (a) art posts and text posts separated into distinct feeds, and (b) thumbnails in a grid instead of a vertical timeline. I built a web app to do this but unfortunately it’s single-user (and basically locked to the Azure cloud). In the meantime, Pixelfed works pretty well for following Mastodon artists.
One (small) issue is that it assumes there *is* a client outside of the server. Most server apps have both a web UI and an API, and it’s even possible to build an ActivityPub server with no client API at all (microblog.pub was like that, IIRC). I think the ActivityPub C2S API was intended for servers that worked just like you’re describing, but IDK if anyone ever really implemented it properly.