Beyond manual testing, I feel that we should have a CI setup that tests installs and upgrades. Logging time would be great on the large dataset, as has been a problem in the past. So that people can estimate the downtime with upgrades.
We’ve seen that for a number of things like the MariaDB or PostgreSQL compatibility such a CI plan will be very useful. So beyond formalizing what the release manager needs to test, the automated test in a CI should be our approach
Actually the documentation is technically correct to say to test the upgrade for the major release because by convention there should be no database changes in minor releases, but in this case there was.