If you are willing to compile darktable, it is possible to process .RW2 from DC-S9 using LibRaw and two small patches to it (LibRaw is used as a submodule in darktable’s source tree). I used darktable-4.8.x branch from Github. Here is a patch for LibRaw:
https://github.com/LibRaw/LibRaw/compare/master…sarunasb:LibRaw:lumix-dc-s9
After compiling, set
libraw_extensions=rw2
in darktablerc in order to use LibRaw for RW2s instead of rawspeed.
You can also add noise profiles and WB presets. These are additions to JSON files and can be done either in source tree before compiling or to the working tree post-install.
I got S9 as possibly the smallest “full frame” camera for use with vintage lenses at their intended, “natural” field of view. Here is a sample taken with OM Zuiko 50mm fully open at f/1.4. Minimal processing in darktable/LibRaw from RW2:
