For the ZKB Twint app, it seems to depend on the smartphone model and/or software version:
- Pixel 6 (oriole), with /e/os 3.6 community, bootloader unlocked: The app works fine.
- Pixel 7 (panther), with /e/os 3.6 official / 3.7 official with locked bootloader: It is not possible to complete the registration process, the app is not functional.
I wonder if there is some setting that is different for the two smartphone models, or whether it is a difference between community vs. official. But the app itself can run on /e/os.