Since the release of OpenCore since 0.7.6 the UIScale key can be found in the
UEFI >
Output section in the Sample.plist. Default for this entry is '0'.
View attachment 564651
In older versions of OpenCore 0.7.5 and earlier, there was a NVRAM UIScale entry, as shown below from the Sample.plist from OC 0.6.9
NVRAM >
Add >
4D1EDE05-38C7-4A6A-9CC6-4BCCA8B38C14 >
UIScale > Data > <
01>
View attachment 564652
If I recall correctly, ocvalidate generates an error when both UIScale keys/entries are present in the config.plist. So adding a NVRAM UIScale entry may not work.
You probably need to use the current UEFI > Output entry, change this number to '2' to see if it makes any difference.