Okay trying to understand the underlying need.
Its VPS, so its already have protection from the MSP or CSP. The DNS of your ISP/CSP/MSP handles queries to your server. That is not causing the attacks. You want DNS for your VPC not your VPS, do you have an entire network up the cloud ?
You can protect your Ubuntu via putting it behind a proxy, which just stays there to slow down attacks and lets through the legit traffic.
Please walk me through scenario, why you require Fast Flux DNS. You can hide administrative services on low risk servers on the same VPC or Subnet and mask connections from there.