Well, your bank is the one choosing to prevent your from running it on GrapheneOS. That's my whole point again! We need to regulate that: it should be forbidden to ban alternative OSes!
Now complaining about the fact that side-loading will require a ONE TIME, "annoying" procedure is not helping this AT ALL. It's just "oh no, I could do it with one click, and now I have to do it in 9 clicks, that's terrible, we need to bring it back to 2 clicks because anyway we won't win if we hope to bring it back to 1 click".
I'm exaggerating of course, it is a big problem for e.g. F-Droid (and maybe others?). But my point is that it's just cosmetic, it's not helping the cause. It's not moving us one inch closer to a better world. On the contrary: it's monopolising the attention of policymakers. They already don't understand much, and we flood them with complaints they don't understand (because really, 99.99% of the Android users don't give a shit about side loading, why would the policymakers care?).
The solution is simple: make it mandatory to allow alternative OSes (which is pretty much as simple as making it mandatory to unlock/relock the bootloader, and maybe remove a few other barriers that exist just for locking us in) and making it illegal to ban alternative OSes with Play Integrity (which is what banks are doing). That's all. No need to fight every decision Google makes and still lose every single time.
We need to get our act together and get the policymakers to do the right thing. But to be fair to the policymakers, technical people on the internet are asking for everything and its contrary.