That just made me look at Google Cloud again, and it's depressing to see. At least some types of load balancer do support dual-stack setups, but not if you configure them via GKE with the k8s ingress controller. If you use that one you're out of luck and they maybe now implement it for the new gateway API controller. So if you use GKE and ingress you can configure two of them. One with a static v4 address and another one with a static v6 address. Of course you pay twice then.

You can remove the address(/128) from old instance and assign it in the new instance and it will works just as EIP.

Why?

What are you using EIP's for and the ability to float them?