>>7700713
Sounds like you got it, but for anyone else:

XP-Pen calls it Proportion.
Open the XP-Pen driver app (called PenTablet)
Go to Work Area
Go to Pen Tablet
Select Proportion

Wacom calls it Force Proportions
Wacom > Wacom tablet properties
Launch Wacom Tablet Properties
Under the Mapping tab, enable Force Proportions

Huion calls it Screen Ratio.
Launch the HuionTablet app
Go to Working Area
On the bottom left there is a drop down.
Switch the dropdown to Screen Ratio.

Gaomon calls it Screen Ratio.
Open the Gaomon driver app
Go to Workspace
Select Screen Ratio

https://docs.thesevenpens.com/drawtab/guides/customizing-your-experience/match-aspect-ratios-with-force-proportions