Does Windows Defender run on Linux?

Microsoft does make a Defender product for Linux, but it is Microsoft Defender for Endpoint, which protects Linux servers in businesses, is managed through a company security portal and needs a business licence. There is no home version and no Windows Security panel on Linux.

Nothing replaces it because nothing needs to. Almost all the malware a home user meets is written for Windows and simply cannot run on Linux. Software arrives from your system's app store rather than from download sites, which removes the main way infections get onto a machine, and everything on the computer updates through that same place, so nothing sits around out of date waiting to be exploited.

That is not the same as being safe. Phishing emails, fake login pages and reused passwords work just as well on Linux as they do on Windows, because they attack you rather than the operating system. A password manager and a moment's suspicion before typing a password are worth more than any scanner.

There is one real use for a scanner. ClamAV finds Windows malware, so if you pass attachments on to family who are still on Windows, or keep files on a drive those machines read, checking before you hand things over is a sensible courtesy.