Does MAC have an Antivirus and Malware Scanner on it that owners can check?

The Mac has X-Protect software built-in.

The operating system is on a separate locked, signed, checksummed Volume that is read-only.

Nothing can become executable without your specifically authorizing it using your Admin password.

The idea that a third party, with no special knowledge of the inner workings of MacOS, can somehow provide better protection that the developers at Apple is laughable.

All this after market so-called "protection" software is just 'scare-ware'.

I have never used any 3rd party security apps. Macs have built in protection. See information in: macOS - Security - Apple

and

Protect your Mac from malware - Apple Support

and

Effective defenses against malware and ot… - Apple Community

how do you know that gmail is the SOURCE of those lies?

looks like ordinary criminal activity to me.

What does it say when you click on the "Why am I seeing this?"