For color profiles management you may want to try colord-kde (sudo apt install colord-kde, tested on KDE Neon/Ubuntu 18.04)
Too bad Wacom & Co don't support Wayland at all, Plasma Wayland is so smooth that makes X11 session looks from '90 😔
Some years ago I was involved in the rewrite of the GUI (an entrepreneur paid a KDE dev to work on the whole stack) and at the time everything worked well. Now I can't test the calibration.
About my setup I have a Lenovo Yoga 720 13'' with integrated Wacom tablet and an Intel 620 GPU.
In my experience Nvidia can be really really problematic so I only use Intel now...
Anyway thanks for your efforts in improving the situation on Linux/Plasma
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