Hello,
I have a >10 year old computer and I decided to upgrade vivaldi deb by manual installation. The version of ubuntu is 24.04.
At the moment I opened the newly installed browser, I noticed flickering and the computer froze. I had to hard restart the computer.
I attempted to open vivaldi again, seeing the flickering. Immediately I realized that this has to do with hw acceleration, as I had a similar problem with opera.
With much patience, I opened the menu of vivaldi, went to settings->webpages and unchecked the option: Use hardware acceleration when available. Restarted vivaldi.
Things now are working normally.
Regards!