BangleJS 2 unable to update firmware

BTW overall it is not very clear what was the initial issue you had and what you did and what went wrong before failed update from the IDE (running on PC?) caused the bank0 invalid message.

fresh out of the box it was in the black-text-on-white that goes with the firmware update page.

this does not say much. what was the error? it is normal for the watch to boot into this screen from cold boot, and if you powered it on via button press and held the button a bit longer you could have triggered the progress bar that would stay in dfu mode if you then released the button too early.

Attempted to use the app loader, and it failed to find the bangle. Switched to firmware updates, and kept it plugged in, turned on, and while the firmware updater used - first nRF firmware update and then NRF connect.

what " Switched to firmware updates" or "turned on, and while the firmware updater used - first nRF firmware update and then NRF connect" means?

It may not be important now but it would be interesting to know if there was actually some real issue with the watch initially or you simply used the button at startup in a way that it somehow always stayed in update mode and then you tried various methods to update it and never actually let it boot properly.

It may not be very intuitive so maybe the watch was perfectly fine until you tried DFU from IDE that probably disconnected in the middle and left the firmware corrupted.