As long as the transaction doesn't require biometrics, I wonder if you could have a traditional smartphone (iphone/android) located physically somewhere else, and a self hosted VPN that would allow you to VPN and remote control the traditional smartphone remotely. So you could run the real bank app on real smartphone hardware (no emulation), and not have to carry it having all access through your Linux phone with a remote control client.

The downside is you'd be responsible for the burden for securing this solution, as your banking app would be one of the most critically security data concerns.