You are allowed to use non-Leica lenses on your Leica Camera
All too often someone on a forum or blog will claim that the only reason to even have a Leica is to use Leica’s lenses. Hogwash! While certainly a fine reason, it’s nothing close to the only reason. The idea that one should never use non-Leica lenses on their Leica is nonsense.
I have a few very nice Leica M lenses. I love them and they are my favorites. But I also have some non-Leica lenses in both LTM and M mounts. They’re fun and interesting and unique. They offer a different look than the Leica lenses. Mine are old, and nowhere near as technically capable as the stuff Voigtlander has been putting out recently. I don’t want those, anyway. I already have all the sharpness and micro-contrast and “pop” I can handle. I put older lenses on my M because it gives the photos a different feel. It can be nostalgic. Sometimes an image works better when it’s a little softer and has a smidge less contrast.
Whether you also own Leica lenses or not, go ahead and slap whatever you want on your camera and have fun.
See also: Don’t listen to this guy. Use any lens you want with a Leica