I use Connect for Lemmy. It comes with a "local" view to see all posts for my host Lemmy instance.

It also has "Frontpage" for stuff I'm subscribed to and "All".

i use liftoff, which has this functionality, but it's a bit hidden. On liftoff, you click the subscribed communities button on the bottom bar (looks like a list, 2nd button on the left), click the "The TTRPG network" main list at the top, click "about" and scroll down to "see all" under the "trending communities" section.