Ok… we will see! 
The iodé main dev has noted on the Telegram / Matrix group that there was a change to to SafetyNet / Play Integrity that caused Safety Net to not pass just in the last day(s). It is not solved yet, but it is at least known and verified to be an issue. As they wrote:
Sorry, still the same cat-and-mouse game. Cat: 1, Mouse: 0
But I have reasonable confidence that it will soon be “Cat: 1, Mouse: 1” in due course.
Note that you are right, the higher level of “Play Integrity” will not pass as it does with full Google Play Services (from Google itself, which Graphene uses but in a non-privileged / containerized way).
Many banking apps, etc. will work fine with microG and SafetyNet passing. Besides the (Editable list) Apps compatible with iodéOS list you can also reference your apps’ compatibility using https://plexus.techlore.tech/
I don’t use the banking app of my bank but “Banking4” (not FOSS, from Play Store for 9,90 €) which can be used for many banks. I use it for a “Genossenschaftsbank” in Germany and Paypal. It works with /e/OS and iodeOS. I don’t know If you still need Secure Go to install the bank access in the app. Several years ago I did not need it.