I am definitely experiencing this same issue. I tried to compare to moonlight and color was on spot with moonlight. Before 3.5.5 update, remote play was totally fine. I figured out the workaround: disable hardware decoding in remote play settings on steam deck.
I was able to verify the issue you have. Turns out if you’re doing performance overlay level, it’ll make UI disappear with disabled hardware decoding. This is really major bug it seems. Turn off performance overlay then you will have workable steam deck ui