Just wanted to chime in that I ran into this problem on my Pixel 7. Up until the update around a month ago everything went smoothly. Then I got the No valid OS found error when I did the update. Got it to reboot after a couple tries and it seemed to download and install the update properly. Since then I have continued to occasionally run into the booting issue.
The phone has so far always managed to eventually reboot. Attaching it to a power supply seems to help it happen faster. I'm not technically proficient but I've read up on the process of sideloading and feel I could try that in Rescue mode if it fails and normal rebooting doesn't seem to work. I'm not inclined to experiment with it though just to see what happens.
In the meantime I've backed up onto a flash drive and have taken to avoiding rebooting unless I'm in at home. I have considered if this is related to a hardware failure though the phone being less then a year old and the coincidence of it running perfectly up until that update has made me kind of wonder about that.