I subscribed to this community with alts on the most populous instances:

• lemmy.world
• sh.itjust.works
• lemmy.ml
• beehaw.org
• discuss.tchncs.de
• reddthat
• lemmy.blahaj.zone
• lemmy.ca

So those at least should be covered, but it’s always good to see if people from different instances are correctly federated too