But using Aurora I can install it just fine and it works flawlessly.
(for me, the whole point of using GrapheneOS is privacy and not sending data to Google, so using the PlayStore is not an option)
I'm pretty sure if I try calling my bank or searching the website to confirm the developer's public key fingerprint, there's not going to be any answer. You have to ask Google's servers to give you the APK and trust what it gives you, either via the front-end called Aurora or the front-end called Play Store