The Swiss "Postfinance" app doesn't load. It crashes on launch. This might have started in the previous beta, but I didn't check.
Betas often break online banking apps. I'm actually surprised the UK Nationwide app still works.
I'd think banking apps might be setting specific iOS requirements and some other checks to try and minimise misuse in any way. It's money and banks need to be cautious to safeguard the public who'd be more than willing to sue the bank if something happens to their money using the banking app on a beta iOS that the bank didn't ask or help the users install.
However, I have seen this happen with number changes in iOS than anytime in between, to the best I can recall. Once an app is optimised for a number version say iOS 13, it stands a chance to work throughout iOS 13.x iterations unless Apple brings some major changes.