Did you can to solve this problem? I have a similar error.
I, [2023-07-12T20:27:26.203859 #1] INFO -- : > su postgres -c 'createdb discourse' || true
2023-07-12 20:27:26.398 UTC [55] postgres@postgres ERROR: database "discourse" already exists
2023-07-12 20:27:26.398 UTC [55] postgres@postgres STATEMENT: CREATE DATABASE discourse;
createdb: error: database creation failed: ERROR: database "discourse" already exists
I, [2023-07-12T20:27:26.423480 #1] INFO -- :
I, [2023-07-12T20:27:26.423858 #1] INFO -- : > su postgres -c 'psql discourse -c "create user discourse;"' || true
2023-07-12 20:27:26.599 UTC [59] postgres@discourse ERROR: role "discourse" already exists
2023-07-12 20:27:26.599 UTC [59] postgres@discourse STATEMENT: create user discourse;
ERROR: role "discourse" already exists
Our script was working normally…