Searx (based on Nginx) "Let's Encrypt" SSL certificate is not valid for Safari (iPhone and MacOS), it is valid for the rest of the world

Solution 1:

Your problem stems from the fact that your web server is not sending any chain certificates with your leaf certificate. This is what the SSL Labs test is trying to tell you when it says, "This server's certificate chain is incomplete".

Browsers and other clients have to guess how to verify the certificate you're sending and some are more capable/lenient than others at doing this. Safari is not. This only started happening recently due to a recent Root CA certificate expiration.

In your nginx config, you likely have a line such as:

ssl_certificate  /etc/letsencrypt/live/ricercaalternativa.mydissent.net/cert.pem;

If so, change cert.pem to fullchain.pem and restart nginx. Then re-check via SSL Labs and see what it says about your chain.