I'm still on KUbuntu 14.04LTS but with a considerable number of personal upgrades including Qt4, kdelibs4, kdepim4 (and plenty of other packages through my own PPAs) and the kernel (local build). I also have a separate, cross-platform build+packaging system through which I install quite a few additional things, notably the Qt5 (5.9), the KF5 frameworks, some KF5 Plasma5 parts and lots of KF5 Applications. This is part of cross-platform development I do on that software; it allows me to run the same versions on Mac and Linux, and confirm that nothing I do on either end introduces regressions on the other end.
Long story short, it's about time I start considering my options to upgrade because 14.04LTS support is coming to an end.
I'd like to preserve my familiar, hand-tuned and more-than-good enough KDE4 desktop instead of being "upgraded" to its Plasma5 equivalent because that would leave me with conflicts between my own Qt5/KF5 and the system versions. I also really don't want KDE PIM5 (KMail c.s.) because they moved to using QtWebEngine.
This question has some details on the cumbersome level of "holding" packages during the upgrade, so it's not really the way I'd want to go: upgrade ubuntu without upgrading plasma4
I could start creating PPAs for all the KDE4 packages I don't yet have personal versions of, but that might even be more work. The ideal would be if someone had already gone through this process. I've done a few quick searches on Launchpad but haven't yet found anything (Ubuntu's habit of using "5" in KDE4 package names doesn't help here!)
If anyone has useful suggestions or pointers, please post!
EDIT: I see there's a kdepim4 package in the current Ubuntu versions, so there's apparently at least a possibility to preserve my KDE PIM4 install in a proper way (if I can find how the matching "kdepimlibs5-dev" is provided; I'd "just" need to rename my own packaging to use the same names).