More diagnostics and a working work-around. One more item from the logs that went with my previous attempts: Nov 29 15:48:26 barley /etc/mysql/debian-start[109190]: /usr/bin/mysql_upgrade: unknown variable 'bind_address=192.168.1.10' In my input there were spaces around the `=`, and so I don't think the problem is that it mistook the whole line for a variable. It may indicate that `bind_address` can only be set on the command line.
I create /etc/default/mariad and put MYSQLD_OPTS = --bind-address=192.168.1.10 in it. This changed the address the daemon listened on. It stopped listening on 127.0.0.1. It is unclear to me exactly how it worked. The file is sourced by the debian-start script, but systemd configuration doesn't seem to run it until after the main command that brings up the database.
