If I read the Dutch news about the ABN Amro KERV ring right, its just the regular KERV ring anyone can order from Kervs website. Meaning it also just uses a Mastercard Prepaid card NFC chip stored inside the ring, NOT a special ABN Amro Maestro chip which would be lots more useful especially in NL, and also wouldn't need constant recharging since it would be connected to a bank account.
Meaning: If you just order the ring from its official website you can probably use it as good (or bad) with Bunq as with ABN Amro. No clue what they thought when they made a PR release for that...