After lengthy tryouts with the Summilux 50 on A7RR, I cannot recommend it without warning. If you shoot at infinity at anything open wider than f:8.0, don't expect sharp corners. Furthermore, the 'Lux will show severe field curvature, and the A7R smears the corner portion of the OOF picture. That makes it a difficult landscape lens to work with at less than, say, f:5.6, and that is not being especially picky either.
Otherwise, the rendering of the 'Lux on A7R is a joy. But it is earned rather than freely given out.