I've been trying to get the app setup today, and I'm struggling to find communities through search. It seems like the search is only checking communities on my instance, not everywhere? Not sure if I'm missing something but I can't find a way to search the broader fediverse.
That is a Lemmy is ran by thousands of individuals who do not want to pay out of pocket to allow every server in the fediverse to waste their resources running search queries all day limitation.
When I search for e.g. "iama", I get several communities from several instances. Seems to work for me. Maybe your instance isn't federating correctly? Or maybe you're looking for niche communities that simply don't exist anywhere? Do other clients/apps work?