Does Sophos work in Big Sur?

The question begs here: why do you want to install that?

Starting with Catalina, the OS and system files are “sequestered” on a read only volume which means that neither you nor anyone or anything else has access or write to it. So why do you want something that won’t be able to do what it says it does?

As others have told you, don’t install tbis or any other “antivirus”, “cleaner” or “optimizer”.

NO, they are not “good” programs.

At best they are useless, at worst they conflict with the system security and make your mac less secure.

Whwdihtdta- wrote:

I don't know anything about that and I was under the impression that Sophos was a good program. So I should not use this at all?

You do not need to use any such program. As I mentioned, the Mac OS and its system files are no longer accessible by anyone or anything - they are on a "read" only volume. In order to install anything, the virus would need to be able to write to it - which it cannot do.

So I should not use this at all?

The OS has built-in protection. You don't need anything else but good sense. How to employ that was posted by jeffreythefrog.

In addition to the algorithms included in the OS, the OS is built on Unix which was specifically designed to be secure on a network. Windows wasn't designed to be on a network, and they bolted on a system to make it work on a network. But, instead of using the principle of least privilege used by Unix, they kept the "everybody has access to everything model." In order to secure that, they must positively block access to certain areas. It is easy to forget to block access. With the Unix model, if you forget to grant access, there is no security issue as there is in Windows.

Why do you want to run something that is completely useless, destabilizes your system, and makes it less secure?

if you're worried about security, please read Effective defenses against malware and other threats - Apple Community. it's a long article but worth reading every word.