I have a 2020 roku soundbar and a 4K Samsung smart tv purchased in 2015. Every few moments the screen goes black and says “no device connected” for several seconds. But the audio continues. This only happens when streaming video, like on Hulu live. I have tried switching the video mode on the tv from standard to movie, I’ve switched the HDMI cables, the HDMI port, unplugged everything and plugged it back in, made sure everything is updated, etc. It’s been going on for months, but it’s only gotten worse with time. It used to flicker occasionally. Now it happens every few moments and sometimes doesn’t go away until I take action.
After a month of this happening, Roku even replaced the soundbar. Still have the issue.