on `Version 5.12.0`
Not sure if this is your area Dylan. Testing should include setting this env variable and making sure the server starts up. I've tried to set other random variables too, just in case. Let me know if you need some example var setting syntax.
Tested and passed on 5.12-release and 5.13-release by folloqing steps provided by Chris.
Setup local server that includes enterprise license
Set variable export MM_SQLSETTINGS_DATASOURCEREPLICAS="mmuser:mostest@tcp(dockerhost:3306)/mattermost_test"
Started the server
Observed: The server started successfully and was responsive.
No update needed to release testing.