Created attachment 144940 [details]
image comparing the regular krita brush (Ink pen at the leftmost corner) with some of the mypaint brushes

SUMMARY
After the 5.0.0 update (and oh boy what a christmas gift it was! Amazing update!) I've been testing the new MyPaint brushes, and a few of them have an issue when using the AppImage (Kubuntu 21.10), the brushes don't do quick strokes nicely and lag behind, leaving weird straight lines, almost if the curve itself was low poly.


STEPS TO REPRODUCE
1. Open up Krita 5 appimage on Ubuntu 21.10/Kubuntu 21.10 with newest DIGImend drivers (10/10.4)
2. Create a document and choose the MyPaint pencil (Pencil 2b Sketch or Ink pen)
3. Quickly draw spheres and spirals

OBSERVED RESULT
The curves on some of the MyPaint brushes don't look proper, it's as if the brush engine lagged behind and couldn't draw them smoothly enough.

EXPECTED RESULT
You should see curves looking exactly how you expect them according to your hand motions.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:  Kubuntu 21.10
(available in About System)
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.86.0
Qt Version: 5.13.0-22 generic (64-bit)
Currently using X11

ADDITIONAL INFORMATION
I've tested the new version on Windows 10 and it works perfectly there without any issues. Not all MyPaint brushes suffer from this issue as seen in the attachment