Lemmy Community Seeder works pretty well. You may want to experiment with which servers you pull from though ( beehaw consistently gave me errors which caused LCS to crash). You can set up a specific account without any admin or moderator privileges if you don't feel comfortable using your personal account (all the account really does is subscribe to the top communities from the servers set in your config). As far as I can tell you only really need to run it once in a while to get an updated list of popular servers.