Error after Drupal 10.1.5 Upgrade: PostgreSQL pg_trgm extension and The version of Drupal you are trying to update from is too old

You should add the pg_trm extension first, that's a hosting issue.

The too old version of Drupal is because it thinks you're missing an update. Will probably need to add debug to find out which core update it thinks you're missing.

This is fixed now after adding the pg_trm extension.

Thanks.