Pretty common around here in WI that they run poly lines in for the main these days. We use a McDonald compression fitting on the poly:
From there, we use brass fittings to hook up the meter, and run copper up the wall to the ceiling, supporting it with bell hangers (there's often a water softener in there, which we also plumb with copper), 90 over, and just get a pex adapter on at that point.
Makes a nice, solid structure for the meter, and it looks nice. I've seen plenty of others' work where they just use pex after the meter, and let it flop where it will, though. Lol
Otherwise, I think the only other fittings you can use on poly are barbed fittings with hose clamps on them.