State and plans of Membrane on Plone 5.2 (Python 3)?

I am currently checking the options for Membrane under Plone 5.2/Python 3 for a large university site.

In particular

Is actually anyone using/working/porting on these modules?

The primary source of update/migration states should be

As for Products.Membrane you can see there @cillian (may you take over here?) worked on this already, but the state is unknown .

collective.castle is not on the list, so it would be good if you add it there. If you start working on it, please link the Issue/PR tracking it.

I had a look at it, but didn't get far enough to open a PR. I was attempting to replace the AT based tests with Dexterity tests but didn't get to a useful point. Unfortunately, I doubt I'll get a chance to look at it again soon.