Remember Gimp --> GTK? And Gimp is still limping on Gtk2 and blurry on each and every scaled Wayland installation.
Who knows, maybe GIMP will jump straight to Gtk4.
There's a good roundup of happenings in 2017 in GIMP here:
https://www.gimp.org/news/2017/12/31/gimp-and-gegl-in-2017/
[EDIT] There are links in the above doc to sponsor GEGL developers [/EDIT]
It's encouraging that GEGL is seeing use in other projects and receiving patches, maybe the GEGLisation isn't too far from completion.
We are simply not in a position to do centralized crowdfunding.
meanwhile Krita: "We can probably postpone worrying about Wayland on Linux for another year" https://krita.org/en/about/krita-roadmap-2017-2019/ >_<
That being said, I have a Monoprice tablet I use through libinput. I used the wacom driver for a bit but libinput gives me enough to do what I want (I have to say having to do matrix math to constrain the screen size so the tablet is in 1 to 1 correlation to the screen was a bit rough on the UX front). Libinput is pretty feature complete on tablet support in the basic use cases, it is just missing a bunch of the tunables from xsetwacom. The Digimend project has done an amazing job providing driver support for a lot of non-wacom tablets as well. It will be interesting if its Wacom tablets that are the pain point on Wayland. I don't have or know anyone with one to confirm or deny if the libinput support is up to par.
If I had the confidence to know what I'm doing (and I don't, I've never touched the Kwin / Wayland / input stacks on Linux at all) I'd try wiring in tablets to Kwin, but you probably want that first - which is still at least a release or two out at best - before you even think about trying to port your KDE Painting app to Wayland.
Why not provide a --no-tablets-i-just-want-wayland option that would not force the X backend?
So turns out it's easy to turn off X11 in the build files https://github.com/myfreeweb/krita-wayland/commit/8ab43e3e1c... and it does work on Wayland now!
If Krita can replace Photoshop for the most part, it's a good alternative on Linux.
Also, if you can put up with the UI for the plugin, the G'MIC filters contain some cool stuff. You can do frequency separation and content aware fill.