kaezone

afaik theres lot of homemade/3d printable adapters for the major systems to adapt to lots of other ones but i haven't looked into it very much myself, other chostheads should have a better idea !!

The thing that makes it practical or impractical to adapt lenses from one mount to another is the "flange distance", how far the back of the lens is from the film. You can adapt lenses from systems with a big flange distance to systems with a smaller flange distance, as long as the difference is greater than the physical thickness of the adapter.

So, for example, you can take a Nikon F-mount SLR lens and adapt it to use on a Canon SLR, but you can't do the opposite without losing infinity focus. F-mount had one of the larger flange distances, so those lenses adapt to a lot of other systems, physically at least.

If buying a film camera with the intention of using lenses from other mounts, you'll want to pay attention to things like, will you be able to use the body's metering function (if any), and will you need to stop down the aperture manually every time you shoot. In the case of rangefinders, you also have to worry about the focus mechanism.

Given that most film SLR bodies are pretty cheap these days, there's really no reason not to get two or three of them so you don't have to worry about adapters. If you want to get into rangefinders it may be a bit of a different story since Leicas and whatnot hold their value better due to collectors.