There are some more or less standard mounts from early days of film: LTM, 42mm, even Pentax K has been shared by numerous manufacturers. There is the m4/3 mount for digital which is shared across several manufacturers.

The problem is that the mount is always a design constraint. The LTM mount means your lenses cannot have AF. The M4/3 mount means that your sensor size is maxed out at 1/4 the size of a full frame camera. Using the Pentax K mount means that you can't ever have a piece of glass closer than 45mm to the imaging surface.

The most interesting manuever might be Nikon's new Z mount which has the closest flange distance of any full frame mount as well as the widest diameter. This makes it so that it is compatible with the largest amount of lenses of any mount when using adapters. Bizarrely, I can use old Canon EF mount lenses with new Nikon cameras with more features than I can using old Nikon lenses from the same era!