If a user asked me today, I would tell them to test the following paths before attempting it in production: - 2.1.x ---> 2.1.latest ---> 3.11.latest ---> 4.0 - 2.2.x ---> 2.2.latest ---> 3.11.latest ---> 4.0 - 3.0.x ---> 3.0.latest ---> 4.0 - 3.x ---> 3.11.latest ---> 4.0
The upgrade paths from 2.1/2.2/3.0/3.x to 3.11 are well-established and known today although the procedure isn't documented on the Apache website. I'd be happy to get drafts in if there are no objections. Cheers!
