Until you manage to find a 3080, you should try switching to a DisplayPort cable. It’s got more bandwidth available than HDMI 2.0, which means that you’ll at least do better than YCbCr420 for colour.
YCbCr420 reduces picture quality because it shares a certain amount of colour information for each 2x2 block of pixels. This makes it a lot harder to show accurate colours. YCbCr422 is better because it halves the height of this block (2x1 pixels, i.e. 2 pixels on the same row), and YCbCr444 gives each pixel its own colour information.
A DisplayPort cable should be able to get you YCbCr444 or pure RGB when you do 4K @ 120Hz. However, you’re unlikely to get 144Hz or HDR because the 1080 lacks support for display stream compression, and you compression to fit the required data down a DisplayPort 1.4 connection.