It might take a while since it's dependent on internet speed to download the flatpaks and sign the image. Should show up eventually even after a reboot. Did the Bazzite Portal also appear on the 2nd reboot?
So will I get any sort of notification when my OS updates, or will I just boot up my PC one morning and find out it downloaded an updated image some time the day before?
Hm, I've seen a popup about checking for updates, but never anything else. I guess maybe there just haven't been any in the last few days? (apart from flatpaks in Discover, of course)