I definitely think this would be a huge value add. The decentralized nature of lemmy makes it so that there are a lot of different communities on different instances, that all are about the same topics. As an end user, it makes sense for me to want to see posts from all these communities in a single feed.
I saw that there is some work on the upstream lemmy side on providing support for multireddits/custom feeds, but upstream discussion also seems to indicate that different frontends, like Boost, should have the apis to be able to do this client side in the meantime.
Related:
- Support for grouping communities / multi-communities · Issue #818 - GitHub https://github.com/LemmyNet/lemmy/issues/818
- https://github.com/LemmyNet/lemmy/issues/3950
Do they have a standalone app?