(In reply to Thorsten Kukuk from comment #1) > This looks like the same problem as all non-webbrowser based tools we have: > > kukuk@f05:~> curl https://defiant.thkukuk.de > curl: (60) SSL certificate problem: unable to get local issuer certificate > More details here: https://curl.haxx.se/docs/sslcerts.html Thanks for help. In the case of seznam.cz, I can get it via curl: $ curl -v https://seznam.cz * Trying 77.75.74.176:443... * Connected to seznam.cz (77.75.74.176) port 443 (#0) * ALPN, offering h2 * ALPN, offering http/1.1 * TLSv1.3 (OUT), TLS handshake, Client hello (1): * TLSv1.3 (IN), TLS handshake, Server hello (2): * TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8): * TLSv1.3 (IN), TLS handshake, Certificate (11): * TLSv1.3 (IN), TLS handshake, CERT verify (15): * TLSv1.3 (IN), TLS handshake, Finished (20): * TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1): * TLSv1.3 (OUT), TLS handshake, Finished (20): * SSL connection using TLSv1.3 / TLS_AES_256_GCM_SHA384 * ALPN, server accepted to use h2 * Server certificate: * subject: CN=www.seznam.cz * start date: Aug 9 14:01:43 2021 GMT * expire date: Nov 7 14:01:41 2021 GMT * subjectAltName: host "seznam.cz" matched cert's "seznam.cz" * issuer: C=US; O=Let's Encrypt; CN=R3 * SSL certificate verify ok. * Using HTTP2, server supports multiplexing * Connection state changed (HTTP/2 confirmed) * Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0 * Using Stream ID: 1 (easy handle 0x557325389bd0) > GET / HTTP/2 > Host: seznam.cz > user-agent: curl/7.79.1 > accept: */* > * TLSv1.3 (IN), TLS handshake, Newsession Ticket (4): * TLSv1.3 (IN), TLS handshake, Newsession Ticket (4): * old SSL session ID is stale, removing * Connection state changed (MAX_CONCURRENT_STREAMS == 128)! < HTTP/2 302 < server: nginx < date: Fri, 01 Oct 2021 11:49:11 GMT < content-type: text/html < content-length: 138 < location: https://www.seznam.cz/ < <html> <head><title>302 Found</title></head> <body> <center><h1>302 Found</h1></center> <hr><center>nginx</center> </body> </html> * Connection #0 to host seznam.cz left intact While I can confirm curl https://defiant.thkukuk.de really does not work for me. So, it's maybe something different?