Fun fact, one of my banking app prevents me from launching it if I do not use a "certified" keyboard app. I had bad luck with any keyboard from F-Droid.
Banking apps are such a disgrace. Full of weird ideas about what is ok and what is not and which data and whatnot they need or else they won't run and in the end it doesn't help at all.
My bank recognizes the risk that third-party keyboard apps pose, and has their own keypad in their authentication app.
The same bank has a maximum password length of 8 characters, and they'll truncate longer passwords without informing the user -- set the password to "correct horse battery staple" and you'll be able to log in with "correct ". When I pointed it out they recommended setting a shorter password.
And for good reason. It's the operating system that should offer a 'certified secure' keyboard if the app requests it though. A bit like Windows' account password entry screen that is sandboxed from the rest of the OS (if I understood it correctly).
In this case, the app has its own keypad when logging in so I'm not sure what the added value is security-wise.
I'm just not able to launch the app while an F-Droid keyboard is set as default which is just annoying. There's many keyboards on the Play Store that I wouldn't trust to install and use.
Well, one of the banking app that I use is really well done (the other one is garbage), it makes my life really easier and has QR code payments included which is how I pay everything online in my country (Belgium) instead of having to use the card reader and it's also how I reimburse my friends if I owe them money.
And it has NFC payments that does not use Google Pay which is also nice.