But we don't have anything like FF as an alternative to go from Android. Especially considering banks require "certified OS".
I also switched banks so I can use my bank card as the 2FA device, similar to CAP. [0]
[0]: https://en.wikipedia.org/wiki/Chip_Authentication_Program
Just observe that the key factor is to be independent from Google and then the only recommended devices from their side are exactly google devices where nobody here can have an idea of what is modified inside them.
You'd be better off supporting other distributions like Calyx, which have no problems in supporting other devices like the fairphone and so on.
They even tell you in their usage guide that it's more secure to use Google's app store than e.g. F-Droid (which neglects several good security practices for an app store), and that it's not a good idea to blindly aim for "degoogling" at all costs.
Go away with your baseless FUD.
The biggest thing that excludes most phones from supporting GrapheneOS is the lack of unlockable bootloader. Pixel phones also allow the developers to target a large but homogeneous hardware base.
The second big thing is that the "non-exhaustive list of requirements" is basically "whatever new Pixels do". Your conclusion that Pixel phones are "the only ones with secure enough hardware" is overstretching what's happening here.
The developers took the Pixel as a template because it's a well selling line, with good security, and generally with unlocked bootloader, and modelled the requirements based on it. It's a reasonable approach to the development of a niche security oriented OS because: "In order to support a device, the appropriate resources also need to be available and dedicated towards it". It has the downside that it makes it sound like no other phone has comparable security features.
Are the fully supported Pixel 6/6a more secure than any other non-Pixel phone sold on the market today?