You are not SOL, by any means. You just cannot use those lenses with DSLRs, as you've discovered. Any DSLR adapters for them will either require image-qualty-spoiling optical correction, or without optical correction will not be able to focus farther than a few feet. This is true with ALL vintage rangefinder lenses... not just m39. They just aren't practical to use on any DSLRs (just as those lenses weren't usable on film SLRs).

Certainly, you could use them on various modern Leica digital "mirrorless", with an M39 screwmount-to-Leica digital L-mount (no optics necessary). Digital Leica are available in both APS-C and full frame models, but are VERY pricey.

Alternatively, you can adapt and use them on most current mirrorless camera.... Sony (APS-C or full frame), Canon (APS-C.... coming next month, full frame ), Nikon (coming soon, full frame).... Fujifilm (APS-C).... Olympus/Panasonic (micro 4/3). These will require m39 screwmount-to-whatever adapters, but those won't need any optics to allow the lens to focus all the way to infinity, just as it was originally designed. (Note: there likely won't be adapters right away for the new full frame models coming from Canon and Nikon.... And there's also rumor that Panasonic will be introducing a full frame model soon.)

The "register" or "lens flange to film/sensor plane focus distance" of Leica m39 screwmount lenses is 28.8mm. Leica bayonet film rangefinders use 27.8mm (leaving 1mm for screw-to-bayonet adapters).

ALL the above mirrorless use shorter lens register.... ranging from 20mm (Canon RF) to 16mm (Nikon Z)... allowing plenty of room for adapters without need for any optical correction.

Also, many mirrorless use an electronic viewfinder. These have features to help with manual focus, such as "focus peaking". This is not found in the optical viewfinders of DSLRs, most of which are designed with autofocus in mind and have little to no assistance for manual focus. Some DSLRs have Focus Confirmation or focus peaking in Live View mode. But, it's a moot point, since ALL DSLRs use much longer lens register, leaving no room for adapters without optics or that will allow infinity focus, with short register vintage rangefinder lenses.

So... take your pick from the crop of mirrorless cameras available. (The only mirrorles I can think of that won't work is the Fujifilm GFX, which is a medium format camera. It has short register, too... but requires lenses with a larger image circle than m39 lenses are able to produce.)

Personally I plan to buy a Canon M5 in the not too distant future. One of the reasons is because it will allow me to use many vintage lenses in my camera collection (albeit, with 1.6X "crop", due to the camera's APS-C size sensor). Among those are several m39 lenses.... and I've already confirmed adapters are available for them (as well as a variety of other vintage mounts). Those simple adapters are pretty inexpensive, too ($25 to $40, for quality m39 to Canon EF-M adapters).

Hmm. It is true that you will not be using autofocus with Leica lenses. Now, I do know the Sony A-6000 fairly well, and little or nothing of the 4/3 cameras. But I do point out that that the Sony has a nifty focus magnifier for using manual focusing lenses,, with two different levels of magnification allowing critical focusing, AND two other and different options to show you how well focused a lens is - I mean besides simply seeing the image sharp on the screen or in the viewfinder. I do use manual legacy glass on mine so I do use manual focus and know of what I speak.

I do also point out that the Sony has a 24 megapixel sensor.

I think you will be hard pressed to find any reasonably current digital camera that does not offer auto-focusing, but although they do not promote it, Sony is about as good as they come for assisting manual focusing.

Cheers

Bob Locher