My Sony a7RII has an Arca-Swiss compatible Sunwayphoto DP-39 (now DP-39R) permanently attached to it. That plate has an opening suitable for a typical 3/8 inch camera strap.

This plate is square so it will mount in a Arca-Swiss tripod ballhead in one of two orientations or, as seen here, it is attached to my Sirui monopod head.

This also shows the male portion of the extremely strong and safe ‘Double Lock Rock Lobster’ buckle which attaches the a7RII to my sling strap when not on a quick release ‘head’.
This 1” clasp has a working load of 120lbs (55kgs) and has the added advantage of an extra safety lock in the center.
I grasp the sling strap female portion with my left hand, squeezing the two release catches with thumb and forefinger awhile grasping the short camera attached section with my other hand. The right hand thumb pushes that center release.
The camera is always firmly held by that right hand and can’t be released by accident.