Does not have to be installed. See this: https://learn.microsoft.com/en-us/azure/defender-for-cloud/c...

A cloud provider can take snapshots of running VMs then run antivirus scan offline to minimize the impact to the customers.

Similarly, many applications are containerized and the containers are stateless, we can scan the docker images instead. This approach has been quite mature.

To say nothing of enterprise EDR/XDR solutions that have linux versions. These things aren’t bulletproof but can be 1 layer in your multilayer security posture.

don't most people who use that just use it for scanning incoming email attachments usually?

ClamAV also has a lot of findings when scanning some open source project's source code. For example, LLVM project's test data. Because some of the test data are meant to check if a known security bug is fixed, from a antivirus software perspective these data files can be seen as exploits. ClamAV is commonly used. Or, I would suggest adding it to every CI build pipeline. Most time it wouldn't have any finding, but it is better than nothing. I would like to offer free help if an open source project has the need to harden their build pipelines and their release process.

In general, my gut feeling is that I expect the majority ClamAV installations to be configured to scan for Windows viruses in user submitted content. Email, hosting sites, etc.