Veritashr website pops-up on desktop after turning on the Mac

Yeah that's just a common scam. Ignore it. "Mac OS Security Center" is as bogus as a three dollar bill.

Phony "tech support" / "ransomware" popups and web pages - Apple Community has a few entertaining illustrations and a more thorough explanation.

Close the window and forget about it. If it comes back, clear Google Chrome's history and website data and / or reset it to defaults: Reset Chrome settings to default - Google Chrome Help

What is "monitor"? How does one start it?

A screenshot may help: Writing an effective Apple Support Communities question - Apple Community

Possibly relevant: About those "<app> will damage your computer" messages - Apple Community and / or Stop unwanted Notifications - Apple Community

Ok thanks. So far so good, but are you able to display an image on that Toshiba TV? Refer to Connect a display to Mac mini - Apple Support. It should be straightforward.

I'm not sure if the veritashr.com website that appears is related to it or not. If the Mini is displaying to the TV correctly, then let's approach that as a separate problem.

I don't believe this site can accept a HEIC image. If you can find a way to convert it to JPG or PNG that will work. The Appendix in Writing an effective Apple Support Communities question - Apple Community describes how to capture screenshots, which will also work. They won't be HEIC.

You're very welcome Bill.

Glad you're enjoying your new Mini, and that you found this site helpful. The depth and breadth of knowledge available here exceeds that of most Apple Geniuses.