Hello
Postgresql version 12.4.3 does not exist. There were releases of versions 12.3, 12.4, 12.5 and no something like 12.x.y. Are you sure you are using postgresql and not any fork?
Also postgresql will report "database files are incompatible with server" (with corresponding details about mismatched values). I cannot find the text "old version of the database format was found".
regards, Sergei