I frequently run across iDEAL QR codes (especially since mollie.com, a frequently used payment processor in the Netherlands, uses this). My natural instinct says I should scan the QR code with the bunq app. But I know that I've tried this before and that this won't work.
Considering that some people are less familiar with how QR codes work, they might not realize this and they'd be left wondering why they're unable to pay.
I think it would be nice if scanning iDEAL QR codes was supported by using the same QR scanning UI already available in the app.
For the record, I know that this is currently implemented in the Rabobank app. So that at least makes me hopeful that this is not impossible.
By the way, at the moment if you scan an iDEAL QR code using the bunq app, haptic feedback goes haywire. So that surely must be a bug.