Well, it is bleeding edge and you probably know that linux needs some time to support that properly. The integrated graphics is a non-issue here: Neither X299 n

Well, it is bleeding edge and you probably know that linux needs some time to support that properly. The integrated graphics is a non-issue here: Neither X299 nor X399 processors have any. You have to combine them with a gpu, and then are free to chose one that is properly supported. For what it's worth, the RX line was the first gpu ever that had proper working free Linux drivers on release (but the stronger versions like the RX 570 or 580 are not in stock or overpriced, thus not a reasonable option right now). I'd expect the RX 550 or any of the older AMD gpus with the mesa driver to be a good choice, but it depends on what you want to do.