LocalWP not secure

I checked with our Local devs on this, and they reminded me that the issues you’re facing have already been on our radar, and bugs have been filed. Specifically, there is an issue with Firefox not trusting our certs, and then there is another bug with our Open Site widget not opening directly in HTTPS. As mentioned, both of these have been filed with bugs for the team already so for now, your best bet will be to utilize a browser other than Firefox and manually update the HTTPS protocol as you have been.