After I updated to macOS 15 my internet connection went out the window. Now with my Centurylink DSL slow internet is not uncommon I just reboot my DSL modem and that fixes it. This time however my connection was normal but places like YouTube would not load. Finally YouTubes diagnostics directed me to reboot. So I did and now everything is OK. What I noticed on my sign in was a extra option for someone other than me to sign into the Mac Studio, that option was not there before. I suppose what ever passes for error correction in the macOS must have fixed something in the reboot. From my Windows side whenever I have an upgrade like this do a complete reboot. I am going to have to get in the habit of doing this on the Apple side as well. This is the first major upgrade I have had with my Mac. Not nearly as scary as a Windows update of this type.