Most Accessible Banking Apps, or experiences with Ally Bank?

I haven't tried all the features of it, but I've been able to do just about everything I've needed to do in the Chase app.

I have tried the following apps and websites.

1. Wells Fargo
2. Capital One
3. Chase
4. Ally

I will caveat this by saying that I only use Capital One and Chase for credit cards,, but it's the same app.
Of the four listed above, I have found Ally, both the app and website to be the most accessible. I have not tried mobile deposit with that app, because I get a paper check maybe once a year!
The rest are accessible, but the interface can be clunky with Voice Over in different areas. Chase, for example sometimes uses annoyingly long webviews that can be slow to scroll through. Capital One is mostly really good, but has a few places where focus gets a bit off when the page scrolls. Wells Fargo is also mostly good, except for a few places where the content is long and or busy. I also have never been successful at capturing images for a mobile deposit independently, even though it attempts to give guidance.
And, as you mentioned, Ally's interest rates are much better than most.

Good luck with your choice!

Though I can't speak to interest, I've had great accessibility luck with the Chime app and find their feature set incredibly helpful. That said, I've never tried to snap a check, maybe someone else can speak to that?