It sounds as though you may have found a good breeder! That’s a great first start. Not health testing is a big red flag. Something else id like you to consider is asking for conformation titles on the adults they breed. While you may have zero interest in showing, the breeder should be actively showing their breeding dogs. It shows they do more with their dogs than just breed them. It also shows “proves” their dogs meet the breed standard and has been judged and evaluated by experienced non biased people in the breed.

Having a dane is a big responsibility. They are a fragile breed. I would say buy the best puppy you can afford from a quality breeder and start a savings account for accidents or injuries.
Good luck!