I'm sorry you're having this trouble. If it were me, I would try clearing the cache (with the tv on):
Hit HOME 5 times.
FAST FORWARD twice. (Clears cache & tv reboots itself. Be patient. It takes 1-2 minutes for the tv to go black, and come back)
That sounds like it's fixing some different problems. Worth a try.
If that doesn't change anything, assuming you can't see menus, look for the pinhole reset button in the back of the tv. Hold that down for 30 seconds (I'm not clear how that's supposed to be used, or if it's the same for all tvs. Your manual should say how to use it. Like so many things Roku: some people say using it differently, in an almost superstitious way, works when the official way didn't. Like, unplugging the tv, and holding the pinhole button while plugging the tv back in. [On a full moon. I don't know.]).
If the tv goes into setup mode, try telling it you don't have internet (you'll connect later, but don't). That will put you in a basic, seemingly-older version of the software. (The antenna tv is vastly different, like it's older.). You could watch antenna tv for awhile, and see if the tv shows a picture. Or, stream through HDMI. If you don't see the problem, then setup the internet connection (home>settings>internet). It may update immediately, or it will take 1-2 days. (You can go to the system>system-update menu.). If it all goes bad again, you'd know that you were affected by Roku's untested update (like so many others). You could salvage your tv by resetting again, and streaming through HDMI. Streaming sticks are cheap. I'm using a $22 stick.
If the setup doesn't put you back to working tv, I'd say it's a hardware problem. It's easy to blame Roku. They definitely don't care about customers, or how updates break tvs. But, still: hardware does fail. It could be as simple as that. Not a bizarre full-moon problem.
"People are often amazed at how much we’ve done with the number of engineers we’ve got." (Roku CEO Anthony Wood, Austin Statesman, Oct 4, 2019). "Amazed" is one way of putting it.