You can get DBS without bank letter - please see following which shows different routes to get DBS:
Haven’t heard from you since, @Bayu. Have you sorted out your employer’s document request?
To be clear, there isn’t an account opening letter with Monzo, unlike conventional banks. You’ll simply get your debit card.
Andrew (@RossA) very helpfully provides the official document list. Does that help you?
Thank you, it has been resolved.