1. Use the RSS client of your choice
2. Go to a master list of all federated Lemmy communities e.g. https://lemmy.world/communities/listing_type/All/page/1
3. Click through to any community on any instance that looks interesting and add its RSS feed to your client.
I don't know precisely what the future of Lemmy will be, I wish them well because they've produced a cool piece of software which is more open than Reddit and puts RSS front and center. But for the time being I simply have some Lemmy feeds right next to the old.reddit.com feeds in my RSS reader, pure win for me as a user. My universe grew and I don't have to have a horse in anyone's race. This is why we RSS.