Currently running 3.3.7 and most things are working pretty well. Want to upgrade to 4.2.2.
I am not sure if my original CMS installation had MySQL 5.6 or 5.7. Is there a way to tell?
To tell which version of MySQL you have now, look in the docker-compose.yml file and it will show you the MySQL image version.
If you think you may have run 5.6 previously and not done the steps in the link you provided above, then running mysqlupgrade again by that route won’t hurt anything.
Then yes you can upgrade to 4.2.3 from 3.x in one step.
The docker-compose files we provide will upgrade MySQL as well at the right time. MySQL 8 upgrades itself from 5.7 so there’s no manual process required.