If your staging/production site is already updated to PG 15, you can pull a backup from there.
Alternatively, you could try to manually update your local data files. This might help:
cd discourse mkdir data/postgres_new docker run --rm \ --entrypoint=/bin/bash \ -v "$(pwd)/data/postgres":/var/lib/postgresql/13/data \ -v "$(pwd)/data/postgres_new":/var/lib/postgresql/15/data \ tianon/postgres-upgrade:13-to-15 \ -c "apt-get update && apt-get install -y postgresql-13-pgvector postgresql-15-pgvector && docker-upgrade" mv data/postgres data/postgres_old mv data/postgres_new data/postgres docker run --rm -v "$(pwd)/data/postgres":/postgres \ discourse/discourse_dev:release chown -R postgres:postgres /postgres (If you’re using an ARM-based processor, you’ll have to build your own image.)