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.