The example given of the UltraHDMI also has the bright areas without scanlines so I tried to make it look like that in the images I posted. You can increase the scanline strength so that bright areas still have scanlines.
I am using a simple comparison to increase the contrast between dark and bright scanline pixels so its not possible to have the dark areas use 2 scanline and bright areas use 1 scanlines for example. I should probably name this feature Scanline contrast.
I have it running on the OSSC and added a Low and High setting. Here is a comparison on lineX3 with scanline strength set to 100% with contrast Off, Low and High:
Here is a lineX3 capture of scanline strength 81% with contrast High: