Photo Ninja & Irfanview, in this case. Both install and run flawlessly under Linux Mint 19.3, using the Windows setup file(s). Darktable or RawTherapee might be alternatives and the laptop carries both as native Linux programs. Then there is the "GIMP" if one can stomach it.
The nice aspect about photo Ninja is that it can deal with RAW files from cameras unknown to it; there is no colour accuracy, but making a profile for the given camera can put things straight. Or at least, make acceptable results.
The LAOWA lens here is at the near limit, 19cm, and even at f/11 there is insufficient depth of field to create an illusion of sharpness in the background. One has to be critically precise with the placement of focus since the lens in itself is very sharp. A bit like the 24/2 Nikkor in fact, which also "suffers"from the same problem.
