Another killer features Sync has that (AFAIK) no other Lemmy android apps currently have:
long pressing a community in the community list drawers will open that community in a new activity windows, essentially the android equivalent to open in a new “window”. Use your phone’s app switcher to switch between these “window”. There is even an option to allow you to open posts in a new window as well. Very handy if you want to write a comment while looking for some information in another thread, or if you’re on a tablet and want to pin multiple sync windows on the screen.
Sync will open links to a lemmy post natively instead of in an embedded web browser. Basically solve one of the most complained issue about linking in Lemmy.