Browser redirect to mc.yandec.com
I had the experience of completely uninstalling and then re-installing MuseScore 3.5.2 under Windows 10. On the second installation I found that when MuseScore opened, my system browser (Chromium Edge) would open to a URL at mc.yandex.com, which would never actually load. I determined this was related to the Start Center. Modifying my preferences so the Start Center didn't run at startup fixed it, and manually selecting the Start Center from the menu opened the browser.
Now the interesting part. I went ahead and did a complete uninstallation (including the folders under AppData in my user directory). Then I did another installation, but as I had in my very first installation, I opted to run the tours. Now no opening the system browser to mc.yandex.com. Then, after opting to stop seeing the tours, they were gone and the Start Center still didn't do the redirect.
So it appears the problem only occurs if I do an install and opt out of the tours during the initial program setup. Leaving the tours option on at this point, and then removing it later, works fine.
It's a minor issue, but I would assume it would be easy to fix as well.