Thanks for the ongoing work here and obviously you've had some successes and learnings along the way.
Getting visibility into documentation has a very nice user visible outcome. Serving the needs of the project should be considered part of this.
I see user tests of compatibility added, but to strengthen the position of MariaDB within the project CI on their side is needed wherever possible. This makes it a strong position to maintain compatibility with MariaDB throughout there future development.
Fixing outstanding compatibility would be a good goal too. e.g. on ponyorm it seems only the CAST as JSON would be a problem (but CI would confirm this) since JSON as alias has been there since 10.2.
As seen with diesel they expect more and a number of database using software are making challenging decisions as to what is supported and require more than just a name but some non-duplicated but easy to maintain code to be able to extend MySQL and MariaDB in the future as they slowly diverge.
Other suggestions that need improvement on the CMS front are:
* Joomla
* PHPBB
* SMF