re: Does someone know how to fix that? Trying to self host Mastodon.
Premade images are probably where your problems are coming from. If it keeps failing, try the installation instructions from github on a standard run of the mill Debian 10 (11 has some problems with Mastodon) image
"pissed everyone off in literally record time" - Recommended by 10 out of 10 people who, for some sad reason, have a dedicated column up to watch #fediblock.