I haven't come across a banking app in the UK that doesn't work with GrapheneOS. HSBC insists you use the AOSP or Google keyboards but otherwise no issues.
Santander at least used to not work, I haven't tried it with the new app they launched. The old app certainly wouldn't work and I was told by customer service there was no way to access it on a phone with an unlocked bootloader.
Santander at least used to not work, I haven't tried it with the new app they launched. The old app certainly wouldn't work and I was told by customer service there was no way to access it on a phone with an unlocked bootloader.