I'm having the same issue, not on my TV, but on my computer (iMac OS 11.7.8 Safari 16.5.1). It's worked fine, even yesterday, but today it's on, but only black screen, sound works fine. It's done this before, then self-corrected, and now it's happening again!
On the Roku homepage, the top two rows look normal, all the ones below are darkened, but not pitch black, as you can still see through the black covering, this is pretty odd.