Focal length only affects field of view, and not perspective. A picture taken from arm's length will have the same amount of perspective distortion regardless of whether it is taken with a (35mm-equivalent) 24mm lens, 35mm lens, 50mm lens, etc. The only difference is how wide the field of view will be.
I see you address this in later posts, but @pixelshifter's suggestion that it's the wide-angle nature of smartphone cameras—and not the arm's length perspective—that makes selfies look weird is wrong.
The guy's an idiot. By his reckoning, an 85mm lens can't be a portrait lens, either, because on MF an 80mm lens is normal and 35mm is just a cropped format relative to MF. And then your 150mm MF lens isn't really a portrait lens, either, because it's a wide angle on an 8x10 LF camera, and MF is just a crop of that format.
The only thing that matters is perspective, which is how far away you are from the camera. Pick your preferred portrait perspective (working distance). Then pick a focal length that gets you the framing you want. That's your portrait lens for the format you're using. It could be 5mm on a cell phone, or 600mm for an 8x10 view camera.