I just checked and noticed some flickering in Google search when using Google Assistant. The first result tile was flickering, the rest were fine. What I saw was clearly a software issue, and probably with Google's software. I'm not worried about it, I'm sure they'll fix it.
Maybe I have a fix for you all. It worked for me. I was having the same issues with the flickering. I've seen in other places people say its just dark mode that does it but I didn't try changing that. For me I switched my screen resolution to WQHD+. When you switch to that your refresh rate is fixed and doesn't swap around. Again this worked for me and stopped the flickering and I kept everything in dark mode. Hope this helps! Also sorry I this has been found and posted...I looked and didn't see anything to it.
I tried changing my screen resolution like you said, but it didn't work. (Probably because it is not a note 20 ultra.) I think we will just have to wait and see what Google decides to do. (I guess?