Just by checking https://lemmy.ml/communities one can see the most popular communities of lemmy.ml. The plan here is to list all the alternatives for those from other instances. One can also suggest alternatives to be added here and I update this living document.

• Libre Culture --> ???
• Piracy --> !piracy@poggerinos.ml
• Open Source --> ???
• Ask Lemmy --> !askwomen@lemmy.ca
• Privacy --> !privacy@lemmy.ca, !privacy@community.nicfab.it, !privacy@nrsk.no, !privacy@sopuli.xyz
• Technology --> !technology@beehaw.org, !technology@gtio.io, !tech@links.roobre.es
• World News --> !news@beehaw.org
• Fediverse --> !fedizens@lemmy.ca, !thefedizenenquirer@lemmy.ca, !fediverse@midwest.social, !fediverselore@lemmy.ca, !bestofthefediverse@lemmy.ca
• Science --> !science@beehaw.org, !science@mander.xyz, !science@gtio.io
• Memes --> !memes@lemmy.ca, !memes@sopuli.xyz, !politicalcompassmemes@lemmy.perthchat.org
• Gaming --> !gaming@beehaw.org
• Music --> !music@sopuli.xyz, !music@baraza.africa, !music@beehaw.org
• Politics --> !moderatepolitics@sopuli.xyz, !politics@beehaw.org, !politics@gtio.io
• Programming language communities --> Heapoverflow.ml, jeremmy.ml
• Socialism --> !socialism@midwest.social, !armchairsocialist@lemmy.ca
• Anarchism --> !anarchism@lemmy.ca
• Green --> slrpnk.net, environment@beehaw.org
• Late Stage Capitalism, futurology etc. --> !aboringdystopia@mander.xyz
• Linux --> !linux@heapoverflow.ml, !linux@sopuli.xyz
• Videos --> !videos@nrsk.no, !video@baraza.africa
• Cryptocurrency --> !cryptocurrency@lemmy.ca
• Political Humor --> !politicalmemes@lemmy.ca
• Self-Hosting --> !selfhosting@slrpnk.net, !main@selfhosting.pub
• Anime --> !anime@jeremmy.ml