First of all, I am sorry for the login issues you experienced. I have just disabled the GeoIP filter, so you should now be able to log in to the admin panel without any problems.
Regarding your recommendations:
I went to Appearance > Customize > General > Layout and disabled smooth scroll, then saved the changes.
I also tried disabling third-party plugins to test it.
Unfortunately, there is no change, and the critical scrolling freeze issue still persists.
The test in the video was done using the Brave browser in incognito mode, but I have also tried other browsers (Safari, Firefox, and Chrome) with the same broken result.
Could you please log in now and check the theme to see what might be causing this?