Just here to confirm that I'm having troubles with bunq + Google Pay on my Pixel 4 and 5 as well. The "Add to G Pay" button in the bunq app just won't appear no matter what I try. Google Pay works fine for me with several other banks, which makes this whole ordeal even more strange.

Customer support is still looking into it. But I'm kinda losing hope. :(

Cards should work just fine according to this thread: https://together.bunq.com/d/18866-turkey-bunq-community-travel-tips