Scala 2.12.20 and 2.13.17 recommended.
Pekko is built with recent releases and while unlikely, forcing it to run with very old releases of Scala may lead to unforeseen issues.
Also, old Scala releases won't support the latest Java releases, eg Java 25. 2.13.17 does while there is no Scala 2.12 release yet that supports Java 25, hopefully 2.12.21 will arrive soon.
You will need to upgrade scoverage too but there are releases of scoverage that support the latest Scala releases.
https://github.com/apache/openwhisk/blob/master/settings.gradle#L74-L96
Scala 2.12.20 and 2.13.17 recommended.
Pekko is built with recent releases and while unlikely, forcing it to run with very old releases of Scala may lead to unforeseen issues.
Also, old Scala releases won't support the latest Java releases, eg Java 25. 2.13.17 does while there is no Scala 2.12 release yet that supports Java 25, hopefully 2.12.21 will arrive soon.
You will need to upgrade scoverage too but there are releases of scoverage that support the latest Scala releases.
https://github.com/apache/openwhisk/blob/master/settings.gradle#L74-L96