Well, for plasma5 in a rolling release of debian, the Siduction forums is a good resource. Lots of rough edges in version 5 of kde, an analogy might be in sports, that they changed the numbers of players on the field and the size of goal (or width of the end zone) - what with using QT5 and a totally revamped system. And they are transtioning to Wayland.
It is not my cup of tea, I abandoned KDE near a decade ago because it was getting heavy and and a nasty neepomuk cache bug (stuck into expansion and not fixed for years).
But how much can a small niche distro do with limited numbrs of developers, no matter how great their skill sets. Other than Tanglu; who does debian testing distros, not many.
It is all right to vent steam at the state of KDE5. But if you want to find someone to do a fork of KDE4, LMD(ebian)E(dition) or LinuxMint might be more suitable. After all, they did much work on Mate there. But a KDE4 fork is probably a Xorg future (no Wayland).
But as you say in your last sentence, LXQT just might do the trick, committed to a more universal language (QT5) than Gnome, picking what works of the KF5 tier one apps (that are written solely in QT5), and going forward with Wayland. Considering that they are maybe only 12 main developers, LXQT is not your LXDE of the past. irc on freenode #lxde