… ok ok, irt looks as if I have some more permission issues here, see /var/log/postgresql/postgresql-13-main.log:
2023-11-10 22:07:58.371 UTC [196127] postgres@postgres STATEMENT: ALTER DEFAULT PRIVILEGES IN SCHEMA 'public' GRANT ALL ON TABLES TO 'discourse';
2023-11-10 22:10:18.270 UTC [196160] discourse@discourse ERROR: permission denied for table site_settings
2023-11-10 22:10:18.270 UTC [196160] discourse@discourse STATEMENT: SELECT name, data_type, value FROM site_settings
2023-11-10 22:10:18.313 UTC [196160] discourse@discourse ERROR: permission denied for table users
2023-11-10 22:10:18.313 UTC [196160] discourse@discourse STATEMENT: SELECT COUNT(*) FROM (SELECT 1 AS one FROM "users" LIMIT 20) subquery_for_count