there’s no communities for my niche interests!!!
more like “i want a ready-made community where other people already putting effort into posting cool and intersting stuff, and all I want to do is sit on my ass and shower posts generously with “”“muh upvotes™””“”
On my instance you just click “Communities” at the top and it gives you a list of communities with three options at the top Subscribed/Local/All just like the main feed. Click all and you can browse or search the list of all communities, though the search is not great.
Your instance does need to know about these communities existing first though. For recently created communities on another instance that might not be the case. Which is where services like Lemmy Explorer help.