DBeaver is able to download adapter on first connection creation. No need to symlink anything.
Yes, it's offering to do that, but wouldn't that be for me as a user? Given the AUR exists, I'd prefer to have that installed to give the benefit for all users, and for all programs that would use mariadb-jdbc.
DBeaver offers Database → Driver Manager → MariaDB and I can then get Information on the existing org.mariadb.jdbc:... library, but I haven't worked out how to Add File, or similar to have it use /usr/share/java/mariadb-jdbc/mariadb-java-client.jar instead. But that's a question more for the dbeaver chaps.
It's the Arch package and the AUR package that I'm trying to get to play together, and then the wiki can be updated.