SUMMARY

App suddenly started to fail registering properly pen tablet click/input correctly 
after an update to 6.0.0 prealpha from 5.3.0( Huion tablet used in this case ).
Additionally, it is impossible to SHIFT + CLICK on multiple layers( both mouse and
stylus can't do it )

I ) Pen/stylus click bug

STEPS TO REPRODUCE ( pen/stylus click )
1. Open the software and wait for the homepage to appear
2. With your pen, try to click on any of the menu bar buttons(View, Tools, Window, File, etc)
3. With your pen, still, after opening a simple document, open the brush editor
4. Try to tick/untick any option in the brush editor(sharpness, ratio, size, scatter...)

OBSERVED RESULT ( pen/stylus click )
- The app fails to register the click input, behaving as if it successfully
selects/deselects or selects twice in a row, but in fraction of second. 
- It prevents you from selecting any layer or menu or UI option using the stylus. Including
options from the Brush editor.

EXPECTED RESULT ( pen/stylus click )
- The pen should register input properly, such that when you tap/click only once, it responds
appropriately instead of skipping weirdly your input or failing to register it properly.

II) Multi select using SHIFT + Click bug

STEPS TO REPRODUCE (multi select bug)
1. Have a new open document with at least 3 layers
2. using mouse or stylus, select the 1st layer in the stack; 
3. Hold SHIFT and click on the 3rd layer to select all the layers
between the 1st and the 3rd. 

OBSERVED RESULT (multi select bug)
- Krita just behaves as if the SHIFT modifier key is absent, 
and only one layer is selected

EXPECTED RESULT ( multi select bug )
- multiple layers should be selected, mainly all the layers between the 1st
selected layer and the last selected layer in the layer stack

SOFTWARE/OS VERSIONS
Windows: 10

Qt Version: 
Seems to be Qt6 instead of Qt5 for prealpha 6.0.0