https://www.techdirt.com/articles/20201208/13454345846/apples-failure-to-ensure-backwards-compatibility-big-sur-leaves-developers-quite-sour.shtml

When there's a major OS upgrade, like Apple's recent Big Sur MacOS release, you would hope that an effort was made to ensure backwards compatibility with key apps and services. However, it's now become clear that Apple failed to do so, and a variety of different developers across a variety of different applications have had to scramble over the last few weeks to update their apps just to keep working on the latest version of MacOS. It's always understandable that a few apps may fall through the cracks, but with Big Sur, it's notable just how widespread the reports are of compatibility problems, and just how much scrambling app developers had to do just to make sure their apps continued working. Here are just a few reports of such problems from across the internet.

There are plenty of gripes from users about Starcraft 2 problems on Big Sur found on MacRumors and elsewhere.