Connect for Lemmy currently doesn't have a great community browser (hopefully that will change soon). What instance are you on? If you are on lemmy.world they have a pretty good community browser here: https://lemmy.world/communities. You can filter it to just search local communities (on lemmy.world) or all. Other instances probably have similar community search options.
I have been a daily reddit user since 2008. I had never seen a single Apollo ad or any discussion of Apollo.
Your search results are biased towards what you have browsed on Google.
Also you shouldn't be seeing ads with proper internet hygiene. Ublock origin, no script, vpn if you can. Res will strip out every reddit ad. And I'd highly recommend duck duck go or something more private than Google these days
Reddit admins using that "feature" to post under other usernames perhaps? I dunno if there's a way to check but I wouldn't be surprised if these folks were not actually subbed to the sub that they seem to care so much about.
I don't know anything about the mobile apps for the fediverse, but you can definitely search for communities from the Lemmy web UI (same goes if you're on kbin). If you go to the Communities tab there should be a search field in the upper-right.
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