Virus warnings from AV program I don't have.

PHK

Which browser are you using?

Newcad

These are 'Push notifications' and are advertising spam.

This is a couple of years old but should still be relevant (although browsers do change so the settings may be slightly different now): https://uk.pcmag.com/browsers/90848/how-to-disable-web-notifications

You say that Malwarebytes found nothing which is good, but now run a scan with ADWcleaner it's also from Malwarebytes but is specificaly geared to finding and removing Adware: https://www.malwarebytes.com/adwcleaner

I would also strongly recommend that you add the Free MalwareBytes Browser Guard extension to your browsers which will block any that do try to pop-up: https://www.malwarebytes.com/browserguard
(PS. forget that '$35.99 value' it's just blurb, MBG has always been Free).

Money_and_Travel

PHK said:

Which browser are you using?

 Google Chrome Version 125.0.6422.61

Prism

In Windows go to System and then Notifications. Scroll down and look for the notification you no longer want and disable it.