Best way to become biologically immortal is probably to solve aging directly in your own body via some sort of whole body viral gene therapy.

Then your still mortal and can be killed so you can chose when to go.

My person preference for immortality would be some sort of live un-interupted transition from a human brain to a computationally simulated one. Only if I personally own my own infrastructure though. That way I can ensure I don't get manipulated. Then probably copy my conscious 100x over and spread over geographically. Maybe keep a copy in a extra solar satellite or something.