Firefox утверждает следующее: Websites prove their identity via certificates, which are valid for a set time period. The certificate for altlinux.org expired on 11/16/2024. Error code: SEC_ERROR_EXPIRED_CERTIFICATE
А ещё: altlinux.org 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. C firefox'а теперь вообще не зайти.
Теперь работает.