I have a phone that can be unlocked, and I will lose access to my banking app (among other things I require) if I do so.

If your “partially accurate” objection is that I didn't describe a perfectly universal experience, I will be greatly disappointed.

Vouching your comment from dead to reply in good faith:

your bank’s app sucks, tell them they suck,

and or use the webapp.

Tens of thousands of financial institution apps work A-OK on GrapheneOS,

that is my objection.

That’s good to know. Is there a list? Maybe a vocal community of computer literate people with money could loudly move to banks that do work (regardless of which phone they have).

Apps with Google SafetyNet usage, and or Google Pay NFC dependency to start the app, two common failure modes.

What does “unlocked” mean, here?

Are we talking about root checks? Bootloader unlock?