You need a reverse proxy like nginx or traefik. Your mastodon server is using the web ports. Lemmy also wants to use the same ports. Obviously the can’t both use them.

The solution is to let neither use the ports and set them up on some other ports.

The reverse proxy is then set up as your main “web server”. It will then look at every request coming in and based on the domain name or url requested redirect (or rather forward or proxy) the request to the correct service… mastadon or Lemmy.

I run dozens of services on the same server. And use traefik to sit in front and manage it all.

I’ve been tangentially involved in this. I think if any of the bigger instance operators were to contact derivator to see what can be done to host a gateway, that would really help.

Since it’s a proxy you’d want a reliable entity to host it, who you trust with your credentials. And the only entities who currently make sense would be the lemmy instance owners themselves. Eg. if I’m already connecting to beehaw.org or lemmy.world, I would be okay to point apollo or baconreader to redditapi.beehaw.org.

See here for a list of how people can help: https://github.com/derivator/tafkars/tree/main/tafkars-lemmy