What is the best-practice procedure for rolling back a DMA to an earlier version?
When can/should we use the generated rollback package, and when the regular upgrade package?
Any additional things to take into account in case the rollback spans across multiple major versions (eg 10.1.0 -> 9.6.0)?
Can we roll back between main and feature releases (eg 10.1.0 -> 9.6.10 or 9.6.10 -> 9.6.0)?
I would advise always re-installing the previous version with the appropriate upgrade package. it should be perfectly possible to go from 10.1.x to 9.6.x, although there are some manual actions required with older versions.
To add to this, the help indicates that from DataMiner 10.0.0/10.0.3 onwards, rollback packages are no longer created.