I have the same error, my idea is using command line to find the error
1. logging to postgresql
    sudo su - postgres
    -bash-4.2$  pg_dump od15_br220805 | gzip > od15_br220805.gz
    pg_dump: server version: 13.9; pg_dump version: 9.2.24
    pg_dump: aborting because of server version mismatch
    -bash-4.2$ exit
    ##so obviously is the pg_dump version not matched to the server version
2. change the pg_dump version
   pg_dump --version
       ## pg_dump (PostgreSQL)9.2##
   sudo find / -name pg_dump
        ## /usr/bin/pg_dump ##
        ## /usr/pgsql-13/bin/pg_dump ##
    sudo ln -sfn /usr/pgsql-13/bin/pg_dump /usr/bin/pg_dump
    pg_dump --version
        ## pg_dump (PostgreSQL) 13.9 ##
Finally I upgrade the pg_dump 
now I could backup the postgresql database either from odoo database manager and command line 
        
    
Was this ever resolved? I am having the same issues restoring a backup.