How do I bypass "this connection is not private" warnings in safari?

From this Apple Discussion:

The issue could be about https vs. http, or similar Transport Layer Security URL. Unless it is your own bookmark (you could use http instead, without the expectation of security), there is little you can do about it. Often it is something the site owner must do to fix it (Revoked certificate/old certificate; Mix of https and http in a single webpage; etc.).

I tried all the answers here and was still in the infinite loop described by @brinkdad. I finally got it to work by going into Keychain Access, finding the certificate, right-click Get Info, expand Trust, changed the "When using this certificate" selection from "Custom" to "Always Trust".

I found that after deleting the certificate, and then first opening a private Safari tab and proceeding worked. After it works on the private Safari tab it should work on the regular tab as well.

In my experience, Safari works fine, until it starts doing this. I've learned that once it starts, almost no page I visit is 'approved.' I'm not about to handle every page as a troubleshooting process to force Safari to do what it should do, normally.

So I just force quit Safari and relaunch it. Starts working fine, again. I've also noted I did not have this problem until I installed Wipr and some other ad block plugins that I had tried in the same time frame. So I turn Wipr Off when visiting sites I know might trigger the problem, but which did not previous to blockers.

For those who are having the issue where the warning page reloads over and over such as @brinkdad, check the details of the certificate from the page, then open Keychain Access and find the certificate and delete it. Refresh the page and proceed to access the website anyway. This should install the correct certificate to allow you to access the website.

Press "Show Details", then press "Visit this website" on the bottom, and the "Visit Website" from the pop up.

Note: if you're still getting this issue after installing the cert, try to edit in keychain access app: locate the cert that you just installed and double click to open the cert, expand "Trust" and change "When using this certificate" option to "Always Trust" close it and refresh the page again, it should work.