Bypass disp_cap in the GUI?

You should be able to do that. I used the following method on LE7, but I haven’t tried it on CE.
cat /sys/class/amhdmitx/amhdmitx0/disp_cap > /storage/.kodi/userdata/disp_cap
This will create a copy of the disp_cap in your Configfiles folder.
Use Notepad++ (or edit from SSH) to edit that file and add the resolution/refresh rates you want, according to the format.
Then:
*edit* see post below.
This will tie the disp_cap you created to the one in amhdmitx folder, and Kodi will use that for its resolution list.
Then reboot.

Edit: Now I see that you linked to my own post :slight_smile: I think that it’s a very niche request, I don’t really see the point of 120Hz from a TV box. It does nothing for video, and I doubt it’ll do anything for the GUI, since it’s already plenty smooth at 60Hz. I’m not even sure if the hardware will even support this refresh rate.