(Author here.) TMTP clients maintain concurrent (possibly intermittent) connections to any number of TMTP services, and each service gets its own inbox. So you don't need a separate app instance per service.
Inboxes for a set of related services could conceivably be merged, tho I haven't done any work on that yet.
Inboxes for a set of related services could conceivably be merged, tho I haven't done any work on that yet.