What I did was actually following the instructions that you linked, and it seems to be working.
OPTIONAL: Create a db back up just in case. Change the values in brackets with the one for your database, and remove the brackets:
docker exec -t (postgrescontainer) pg_dump -c -U (usernamedatabaseimmich) -d (immichdatabase) | gzip > (/mnt/user/Data/)immich.sql.gz
Stop immich and postgres
Change the container version on my postgres container. Make sure you choose the right version of pg, in my case it's 15. It's key to use a repo with -v0.2.0 at the end, like in this picture!!!!
Restarted postgres
Opened a shell in the postgres container:
docker exec -it (postgrescontainer) bash
enter the database:
psql -U (usernamedatabaseimmich) -d (immichdatabase)
Run the postgres command (making sure to change the name of the database if needed where it says “ALTER DATABASE immich”)
BEGIN;
CREATE SCHEMA IF NOT EXISTS vectors;
ALTER DATABASE immich SET search_path TO "$user", public, vectors;
SET search_path TO "$user", public, vectors;
UPDATE pg_catalog.pg_extension SET extversion = '0.1.11' WHERE extname = 'vectors';
UPDATE pg_catalog.pg_extension SET extrelocatable = true WHERE extname = 'vectors';
ALTER EXTENSION vectors SET SCHEMA vectors;
UPDATE pg_catalog.pg_extension SET extrelocatable = false WHERE extname = 'vectors';
ALTER EXTENSION vectors UPDATE TO '0.2.0';
SELECT pgvectors_upgrade();
COMMIT;
Restarted postgres container
Restarted immich container