Unfortunately, I have no experience with them, but I've been thinking about opening that account for a long time, maybe in my next visit to Spain I will give them a visit and report back.
According to Santander, "The Mundo Account is a Euro current account with instant access. This account is intended for non-resident individuals who are over 18 years of age," so I guess most of us fulfill the main︀ requirements? 😛
Someone posted this on Reddit 7 months ago, not sure if it's true but︁ somehow encouraging: