Safari cannot play videos on some of the websites such as apple.com and twitter. Erasing disk and reinstalling system didn't work. This problem appears on both Catalina and Big Sur. I guess this is a hardware issue. [MacBook Pro 15" 2019.]
Greetings, zac64bit.
It appears that you're having a problem using Safari to play video content on the web. You've already tried a clean installation of the operating system but the issue is still present. You also states that this has been happening since macOS Catalina. We're glad to help with this.
If Safari is slow, stops responding, quits unexpectedly, or has other issues -- This can be due to Safari Extensions. Turn off any extension you've added to Safari then see if those videos will play. If they do, turn each extension back on one at a time and test between each.
Let us know how that goes.
Take care.
Maybe the videos need Flash. Safari 14.0 dropped support for Adobe's Flash player.
Safari cannot play some videos.
