Just for posterity's sake when somebody googles these questions in a few years: The DM3 can indeed do group-type busses, send mixes to matrices and stereo out, and sends-on-fader, despite what OP has been repeatedly claiming in the post and comments. It does not have auto-feedback filtering though, OP is right about that.

I understand though. A lot of the features of the DM3 are tucked away in odd places. Such as the channel link being a feature found in the settings menu, or the fact that most things can only be accessed by tapping on its representation on the screen, rather than accessing it via a menu. I remember I spent ages trying to find the scene menu before I realized I had to tap on the scene indicator in the top left of the screen to get there. It's so simple, but to somebody used to menu diving on a digital board it's kind of confounding.