I don’t remember an update but the same thing is happening to me, I have tried all the same things and still nothing on the screen, mother in-law got the update same model ultra 4600 and hers is working fine, so frustrating!!
This happened to me too. My unit is now a brick!!!!! I upgraded the Roku Ultra firmware to version 10.5.0 and now nothing streams. I contacted Roku by Chat, tried the Factory reset they told me would solve the problem, waited the full hour and a half for everything to reset and reload my channels and still - nothing streams!!!! It's become obvious that this was a bad software release. Did they not test on every model in their product portfolio? Did they know there were bugs in the firmware but decided to release it anyway? I've already started steering my friends away from Roku if they are going to continue releasing untested firmware. This is ridiculous. I went from a working unit to a brick.
I have 3 different Roku's in my home: Premier 4, Express 4 and the Ultra. Seems the issue is only happening on my Ultra box. I have rebooted several times, un-installed and re-installed the apps. Hulu, Discovery+ and Peacock for sure do not work, I haven't tried other apps yet. My box is connected to the 5G of my Wi-Fi with excellent signal and there is no option for me to try an connect to the 2.4G and see if that fixes it as I have a mesh system and it automatically puts it on the best band.