No. “Half regular” would be 0.5 scale, which GTK does not support. However, none of that should be necessary: 1920x1080 is not a HiDPI resolution. You should be able to set scaling to regular and your font DPI to either 0 (auto-detect) or 96 (default).
If you open the display properties, what is the highest resolution that you see there?
Also, could you run ubuntu-report show and paste the result here?