How to get through security error pages in the Firefox web browser?

I'm aware that we use thisisunsafe in Chrome to bypass such error pages but how can I bypass such pages in Firefox? I get the following error when I load the page:-

Firefox detected a potential security threat and did not continue to <site> because this website requires a secure connection.

<site> has a security policy called HTTP Strict Transport Security (HSTS), which means that Firefox can only connect to it securely. You can’t add an exception to visit this site.

I tried the following steps to resolve it but it didn't solve the issue:-

1. Opened a new tab and entered about:config
2. Clicked on Accept the Risk and Continue
3. In the search field, type in security.enterprise_roots.enabled and hit enter
4. I saw one field which was already enabled true
5. Didn't know what to do next as the field was already enabled true

I'm looking for a workaround of thisisunsafe in Firefox.

1. In the Mozilla Firefox address bar, type about:config
   
2. Look for network.stricttransportsecurity.preloadlist
   
3. And set the last field Value to false and restart the browser.