Well, I'm pretty much okay using fully open Linux called postmarketOS on a smartphone, plus Andbox/Waydroid for (sandboxed!) compatibility with Android apps. That's also a free choice.
On pmOS, there's also full KVM virtualization support (works out-of-the-box on most aarch64 devices) for more picky apps, as well.
You're still essentially using either iOS or Android if you want to interact with many banks. Sometimes they will let you use compatibility layers, sometimes not. (I can't access some bank apps on OxygenOS, which is actual Android)
But anyway. I don't want to start the pointless flame war for the milionth time. I think I just have a different definition of "modern life", which is based on using what was considered high-tech not so long ago, like high-throughput radio links and instantaneous worldwide communication (including things like video), without giving up any control. It's not needed to do the abovementioned, so why would I?
BTW, 90% of internet services of any kind still serves "web apps". Which is far from perfect, but gives best compatibility and security out of all technologies we've managed to push to very high adoption.
On pmOS, there's also full KVM virtualization support (works out-of-the-box on most aarch64 devices) for more picky apps, as well.