This domain is part of Google's 2mdn.net infrastructure, which is used for ad delivery and content serving. The page itself shows a 404 error, meaning it's not meant for direct visits. If you ended up here through a redirect or a broken link, there's no cause for alarm, but also no reason to engage further.
For an infrastructure server, the security setup is acceptable but not perfect—the server still supports old TLS protocols that browsers have dropped, and essential security headers beyond clickjacking protection are missing. That's worth a note, but not a dealbreaker for this type of site.
The bigger takeaway: this isn't a website you can use or interact with. It's a server name in Google's ad network, and the 404 suggests it may have been decommissioned or is only reachable under specific conditions. If you were expecting to find a working site here, you won't. For anyone wondering 'is r3---sn-vgqsknzz.c.2mdn.net a scam', the answer is no—it's just a non-functioning backend address.