Even if you don’t have an iCloud+ subscription, Turn off “Limit IP address tracking.”
See “Turn off Private Relay for a specific network on your Mac” https://support.apple.com/102022
If the error persists, try another DNS server
DNS settings https://support.apple.com/guide/mac-help/mh14127/
Cloudflare: 1.1.1.1, 1.0.0.1
Google: 8.8.8.8, 8.8.4.4
OpenDNS: 208.67.222.222, 208.67.220.220
I can connect to the site in your screenshot - no problems. Given what it seems to offer (I don't read Russian), probably good that you can't get to it.