The default docker compose file from the tutorial on Lemmy's website tries to set up the whole thing with Postgresql 18 image but I got some error with that, i fixed it by using Postgresql 16 image. I forgot what the error message was, but there were people on GitHub complaining about the same errors but one of the devs kept closing them as "support" issue and told everyone to solve it on forums or matrix but people where clueless the as well when i googled around.