Ah, the R4 brings back many happy memories. I took a pair of them with me to China in 1985. Upon entering the country I had to register the cameras (they thought I wanted to sell them) and was told I would have to produce them in order to leave the country again. On arriving at a hotel in what then was Canton, I asked where I could leave the cameras while I went downstairs to eat. I was assured I could leave them in the hotel room - a room with no lock on the door. Naturally I was reluctant but did so. For the entire trip I trusted that the cameras would be safe from theft and was not disappointed. Then I discovered what the penalty was for stealing...Oh, while we are dreaming a little out of the box in the midst of a pandemic, it is time to resurrect my Leica R4. But a lens would be nice. LOL...the lens mount aperture is a little wide and not adjustable for focusing.
I'm all in for Impressionism but it is a bit much without a lens.
I doubt I would be so trusting today.
You might get a lens cheap on eBay if you insist on sharp images. But you'll lose that wide open aperture and gain some weight.