As described here System Requirements the MySQL supported versions for Release Automation 6.8 are:
MySQL 5.5, 5.6 and 8
Is the MySQL version 5.7 supported too ?
Release Automation 6.8
The list of changes done in MySQL 5.7 do not impact Release Automation.
So Release Automation is expected to work fine with MySQL 5.7, and support will be provided if there is any issues with MySQL 5.7
Release Automation 6.9 only supports MySQL 8