UPDATED WORKAROUND
Slightly less tedious workaround in case the mysql-router package is upgraded, for each mysql instance (each instantiation and unit):
sed -i 's/client_ssl_mode=PREFERRED/client_ssl_mode=PASSTHROUGH/' mysqlrouter.conf systemctl restart <app>-mysql-router
UPDATED WORKAROUND
Slightly less tedious workaround in case the mysql-router package is upgraded, for each mysql instance (each instantiation and unit):
sed -i 's/client_ ssl_mode= PREFERRED/ client_ ssl_mode= PASSTHROUGH/ ' mysqlrouter.conf
systemctl restart <app>-mysql-router