Possible to mask server IP address?
8 Gbps isn't much tho. VPN will work but that will cause small ping issues. And obviously VPN doesn't have a game specific firewall. And you were talking about domain protection earlier, which is different. Still it is better to get a hosting with a game specific anti ddos.
On battlemetrics you can buy a subscription and register your server with a domain name.
But this will add 0 security to your server, one can just ping the domain name and obtain the IP.
You can buy a cheap ddos protected VPS(2 cores, ~1gb ram) and install your own VPN like wireguard
I believe Battle Metrics still show server IPs and get them via steam

Yes I am. This is only shown because they have specified the domain in RCON settings on BM (which is paid, and does not really hide your IP)

Simply buy a RUST server located in the OVH data center and you have solved the problem 100% related to ddos attacks.

It is impossible to hide the IP address in the Rust game. You can set up a domain etc ... but the person who wants to do a ddos attack will always find your IP address. The problem was solved with the OVH data center in your case.

"Throw money at it" is not a viable solution for everyone. Just saying.

it's not "throwing money at it" though, getting a good hosting is something everybody should do if they care and if its needed (if you are large, no god please no NOT OVH. but for 95% it likely is enough tho)

I don't think it's fair to say someone doesn't care about their server just because they don't pay a hosting company.

it depends, what I've actually meant is that people should not be selecting random hostings from the internet (instead of getting a proper one) nor underpaying for hosting, at least if current does not offer good quality enough to handle attacks