This is why we need open source cameras - so people don't need to spend 6 years reverse engineering and still not getting much out of it
Might be AXIOM from the Apertus project: https://www.apertus.org/axiom
Levoy called the academic exercise he pursued the Frankencamera. (Look it up, a big thing at Stanford). Nokia took him up on it and produced an OTC "smartphone" ... before the iPhone.
i still have a N900 and it works: replaceable batteries do wonders!-) Runs unix etc. Open source camera software.
I think it would actually make sense to build an open source camera on Android. The android camera HAL and camera2 APIs are pretty good (though limited). You get all the UI stuff for free, and a large dev ecosystem. Halide is great for very fast processing. We used them both for the Ubuntu Touch camera app. Though if you really want to push what's possible, access the more low level features would need to be open source too.
Nokia (or HMD Global) are back in the camera phone game again btw - 5 lens android camera coming out this year according to rumours. I think this type of multi-sensor camera really is the way forward on mobile phones. You can keep the lenses thin with much larger sensor size when combined. I really wish they would open source at least some parts of it, but unlikely
Open source cameras exist. They use chemical processing and have manual controls. The documentation is good and it is even practical to build one's own gear...indeed there is a long tradition. Hacking a Leica film camera just wouldn't be as newsworthy.
In some sense, the low returns smell like an XY problem. To a first approximation, reprogramming a Leica is not going to improve it as a photographic tool. The limitation is the going to be the photographer not the software. For software, there's always post.
Making up developer from base chemicals (metol, phenidone, hydroquinone, and so on) isn't impossible and some people do it so they can "tweak" the process a little bit.
The one thing I've never heard of anyone doing is making up a photographic emulsion from scratch at hobbyist level and coating a film base with it.
There are also well documented photo-chemical substrates that are relatively easy for a radically open source photographer to hack on, e.g. wet plate collodian and the more film like dry plate silver gelatin processes. Not all that practical adapt to a 35mm film camera. But analogously open source jumps through hoops to run on an iPhone.
Make dry plate: http://www.alternativephotography.com/silver-gelatin-dry-pla...