I have almost always merged stable to master, following the documentation at https://community.kde.org/Infrastructure/ GitLab#Switching_the_target_branch_of_a_Merge_Request
Most of what I do is fixing bugs or warts in PIM, so I debug on the release/* branch, and commit there to get the changes out to the users in the next release. I think bug-fixing on master and cherry-picking back to release wouldn't work so well.
