Somebody would have to step in with details on Maven: I'm using Liferay Workspace (gradle based), where I just declare a target platform and don't need to worry about any version - in fact, not even about individual dependency modules: It's only necessary to give a single dependency and the build process figures out the actual dependencies and their versions. I couldn't imagine having to figure out the exact module's name first, then its version, and track the version progress over time.

I've kepy myself at distance from Maven though, so I'm not sure how to trigger the same behavior there (or if it's possible)

I think 8.1.11 is what you need. There's some process I don't understand that makes the version you see in the src code's declared patch level off-by-1. The src code isn't the best way to determine the artifact version you need to reference. You can see this in the tag's last commit message in portal-impl:

 artifact:ignore portal-impl 8.1.11 prep next

Edited to add: to paraphrase Hansel (from Zoolander fame): Listen to your friend Olaf. He's a cool dude.

Using Liferay Workspace's target platform will make your life easier.