Hello Ardour user friends, I find an issue with Ardour on Windows.
iZotope RX 11 Voice de-noise plugin window can’t draw fully on Ardour,
there’s a large areas of white blank.
My display is at scale 150%
How to fix it?
Version of Ardour thatr you’re using?
Is that scaling a setting of MS Windows or Ardour > Preferences > Appearance > Font & UI scaling?
The latter would be passed on to the plugin, if the plugin supports it.
The latest version, Ardour 9.1release
My display resolution is 3840x2160, the 150% scale is Windows OS “Recommended” setting,
Ardour is at scale 300%.
But the maximum scale setting I can set to work
in Ardour is 175% to work with OS display scale at 150%.
If scale setting in Ardour isn’t big enough the fonts and icons would be too small.
Can you narrow it down, if modifying any of these scaling fixes or improves things?
Is it just iZotope, or are other plugins also affected?
iZotope RX 11 Voice de-noise plugin only allows certain maximum scale value in Ardour setting,
once surpass it the problem arises.
I have some other plugins,
they all work well with Ardour and other DAW softwares.
Don’t know much technical knowledge,
maybe both Ardour and iZotope RX 11 Voice de-noise plugin have
the blame for not tying well together?
I don’t know if RX11 uses the DPF framework but at least older versions of that has similar issues with window scaling in Ardour :
Most certainly not. DPF is some free/libre framework. For iZotope to use it, hell would need to freeze over first 
That being said, some plugins have indeed a max scaling limit. Particularly older ones that use pre-rendered images for knobs instead of scalable vector graphics.
and throw in windows as well I hazard a guess that this is due to a combination of using both Windows Desktop/Monitor scaling in combination with Ardour UI scaling.
and throw in windows as well
I forgot to mention the most important actor. 
I prefer to use the maximum display resolution setting,
with maximum display resolution setting I have to use OS system wide scale.
I have tested all iZotope RX 11 plugins in Ardour 9.1,
some work well with the UI, some don’t.