There is a browser extension for desktop Firefox called Mullem which allows for following Lemmy communities, and combining them into feeds called “mullems”, similar to multireddits, entirely using local storage. I couldn’t get this extension to work, though – whenever I’d attempt to view a community through Mullem, it just tells me “File not found - Firefox can’t find the file at moz-extension://[bla bla bla bla]/sidebar/[community URL]”.
If that doesn’t happen to you, or you can figure out what causes this bug, then that might be your answer.