My websites behind UTM are blacklisted by Google - am I able to include the google meta tag in header rewrite?

Just recently I found that accessing my websites (nextcloud and also a wordpress install) through chrome or firefox, generates a warning that they have malware.

I've used a couple of on-line scanners to verify that the sites are clean, and I can't see anything in the logs and the UTM hasn't been complaining.

To fix it, I believe I first need to include a google meta tag in the header of the sites to prove ownership.  I'm using a free sub domain so cannot add the meta tag to the DNS, and I've poked around Nextcloud and am not sure how I would add it to the homepage.  

The google error is;  This site is unsafe:  the site includes pages that send visitors to harmful websites

https://sitecheck.sucuri.net tells me a little more info;

"This page redirects to sitename:443 that is blacklisted by Google Safe Browsing

HTTP redirect <301 Moved Permanently>

It's curious that both sites have the same problem, which makes me think it is something I've done on the UTM to enforce https

Am I able to use the UTM to include the meta tag that google wants me to add to each site (different tags for each site) so I can kick off the process of validating the sites are clean?

I'm open to other ideas if I'm barking up the wrong tree.