I am US-based. I have a handful of credit card apps, and a few banking / investment apps - all of them in my experience have worked fine. ONE of them required me to toggle a GrapheneOS option that enables you to exempt certain apps from some of Graphenes more hardened safety measures.

"Exploit Protection Compatibility Mode" is the toggle which can be flipped per-app, and is very easy to access so you can quickly troubleshoot whether that's related to any app troubles or not.

Similar to the other comment, I also use Pixel Camera by downloading the Google pixel cam APK and installing. I've removed all permissions from the camera (and photos) app besides to the camera lense itself, and file permissions of course. You can even use Pixel Cam's hefty features like unblur, erase me, etc. - though certain ones require you to temporarily give network access to the camera app so that it can reach out and download necessary packages. Once done, you can remove network permissions and the downloaded function will remain functional.

All my bank apps work, I have the stock pixel camera app and it works perfectly

Banking app https://privsec.dev/posts/android/banking-applications-compatibility-with-grapheneos/

I haven't had problems with Canadian banking apps, and I use 3 of them. Sadly, my favourite budgeting app doesn't work with Graphene OS. I use it every day (and have paid for lifetime premium access), so it was unfortunately a pretty big issue. But I love what they do. A cause worth donating to.

I haven't yet tried -- planning to do that in the next day or so when I get the time.

Others already replied with promising results, I sure hope they work for me as well (Scotiabank in Canada is particularly annoying in this respect in my experience, with LineageOS I had to use Magisk and define stealth rules specifically for their banking app).

Edit: As for camera, I've only tried the GrapheneOS builtin/default camera app. It's pretty basic, but I should see if I can get the Pixel9 official camera app on there, it would be nicer to use if possible but the basic one is probably good enough for my purposes.

80% of them works. rest has real devs. they should have a bank and government app list in their forums.