mbin is probably the closest to what you want. Its supports both threaded content (lemmy) as well as microblogging (mastodon) Here is a list of servers https://joinmbin.org/servers and interstellar is the mbin app.
If piefed decides to create an api later, I would prefer they did their own thing and try to be lemmy compatible. Looking at misskey, I think not forcing api to be compatible with the more popular service has many upsides.
mbin is probably the closest to what you want. Its supports both threaded content (lemmy) as well as microblogging (mastodon) Here is a list of servers https://joinmbin.org/servers and interstellar is the mbin app.
Honourable mention to piefed.social / pyfedi which can do both as well.
However, it’s newer than mbin and I’m not sure about mobile apps working with it.
Piefed doesn’t have an api, so no 3rd party client. You can use the PWA.
Someone creates a version which adds a Lemmy compatible api to pyfedi and tested out a couple of mobile apps against it, https://codeberg.org/rimu/pyfedi/issues/13#issuecomment-1814982
So it’s not impossible - but it’s also very much a YMMV thing (I suppose it’s really still only for developers atm)
If piefed decides to create an api later, I would prefer they did their own thing and try to be lemmy compatible. Looking at misskey, I think not forcing api to be compatible with the more popular service has many upsides.
Mbin also works pretty well directly using web.