Glad that works for you! With my bank (comdirect.de) I can use a mobile website, and if I were to use something AOSP- or Halium-based, I could also use their PhotoTAN app, which, as the name implies, needs a working camera in Waydroid (on my OP6 with pmOS, the cameras work via libcamera, but not in Waydroid), so I have a small gadget for all these TANs.
My main worry with the “let’s just use Play Store/Aurora store and the run that apk”-approach is that it does not really send a visible signal to banks that they need to keep considering customers that don’t use Android proper.
It also always means that the next update (e.g., after some consultancy or some audit happened) may not work any more, meaning, access may be revoked at any time. Complaining to customer service or in Play Store reviews may have an effect, but it will still hurt. I think I would feel a tad safer if a banking app lived on FDroid… but sill.
I hope this gets my point across.
In theory, you should just see the same apps in Discover and in GNOME Software, assuming they both can access/install native Alpine and flathub apps. (And I recall they did at some point in time, but breakage unfortunately happens, and I mostly use the terminal to install and remove things…)
With Ubuntu Touch apps it’s different, the Open Store is its own thing. I want to look into whether adapting this to postmarketOS when I can find the time.
Regarding few apps: Yes, it could be more, yes, there are gaps, but we’re doing somewhat okay: https://linuxphoneapps.org/