It kinda depends on what you define as “functional” though. Because depending on that it is definitely feasible to vote with your wallet.

In my case for example, I use a fairphone with lineageos and microg. This means I have to live with some minor inconveniences around banking and such. But, for me, this is a functional device and I can do everything I want to do with it.

By not using GrapheneOS obviously.

Also GrapheneOS is about security not about privacy or freedom. So GrapheneOS is just not really part of the discussion here.

Probably this hard: https://postmarketos.org/