How feasible is it to interact with your bank or other necessary services in a browser vs using the play store app? I can see LineageOS being viable if you can make such a transition.

Understanding that you probably paraphrased for brevity, it’s hard to respond with anything helpful because only you know where the goalposts of, “actually works,” are – same thing with, “reliable push messages,” and, “works for banking.” I’ve used swipe input on the native Samsung keyboard and SwiftKey and found that they work just fine, but not as good as GBoard. If you’re going from a Google-invested product to pretty much anything else, it’s likely going to be a worse user experience, so you just have to set your expectations appropriately and keep in mind that what you’re getting in return for that is intangible but important.

What have you tried so far, and how have they failed you with respect to the metrics you’ve stated?