Everything coming from China is going to be closed source as well, and it's going to be pretty hard for banks to onboard themselves on open source solutions. I think the ultimate solution is: two phones, one shitty one just for banking/trading/whatever, which only stays at home most of the time, and one Linux phone that we more or less own, for calls/texts/web browsing, which stays with us.
The irony is that our phones are unbelievably powerful and run laps around computers from just 5-10 years ago, but then we use them as locked-down glorified web views and advertisement deliverers.
Why? I have the freedom to fix or modify most things I own. What makes phones so special that it justifies licking the boot of some techbro billionaires?