The Setup Assistant says "6/7 complete", but there's nothing else left to do:
At the same time, I can tell that the migration is not complete because it's only collecting events for a seemingly random subset of website pages.
Un-ticking items and ticking them back doesn't help.
My best guess at this point is to create a new property.
Try to go to the UA property and in the setup assistant turn off "automatically set up a basic Google Analytics 4 property". Go back to GA4 and refresh. Should sort it.
If it doesn't work then try to turn off all the adblocker extensions. Then refresh the page so the seventh item, "Turn on Google signals", showed up and you could be able to complete the process. After that mark as complete.