snapper.io is not secure

[ShalokShalom]

Hitting snapper.io from my Vivaldi, it reports the website is not secure.
I imagine the certificate is outdated, or something like that.

I honestly did not have a close look on the exact error, and now my browser is just skipping it and going straight to the site, sorry. :)

[Marcool04]

Yeah Firefox for example is just saying there is no HTTPS version:

HTTPS-Only Mode Alert
Secure Site Not Available

You’ve enabled HTTPS-Only Mode for enhanced security, and a HTTPS 
version of snapper.io is not available.

What could be causing this?

    Most likely, the website simply does not support HTTPS.
    It’s also possible that an attacker is involved. If you decide to visit
    the website, you should not enter any sensitive information like
    passwords, emails, or credit card details.

If you continue, HTTPS-Only Mode will be turned off temporarily for this site.

and it seems the only certificate that can be found is for github.com:

curl -v "https://snapper.io"                                                                                              
* Host snapper.io:443 was resolved.                                                                                                      
* IPv6: (none)                                                                                                                           
* IPv4: 192.30.252.153, 192.30.252.154                                                                                                   
*   Trying 192.30.252.153:443...                                                                                                         
* Connected to snapper.io (192.30.252.153) port 443
* ALPN: curl offers h2,http/1.1
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
*  CAfile: /etc/ssl/certs/ca-certificates.crt
*  CApath: none
* 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_128_GCM_SHA256 / x25519 / RSASSA-PSS
* ALPN: server accepted h2
* Server certificate:
*  subject: C=US; ST=California; L=San Francisco; O=GitHub, Inc.; CN=*.github.com
*  start date: Jul  7 00:00:00 2023 GMT
*  expire date: Jul  9 23:59:59 2024 GMT
*  subjectAltName does not match host name snapper.io
* SSL: no alternative certificate subject name matches target host name 'snapper.io'
* Closing connection
* TLSv1.3 (OUT), TLS alert, close notify (256):
curl: (60) SSL: no alternative certificate subject name matches target host name 'snapper.io'