Aha!, that’s the end of that plan: it appears that I am required to do some programming work on Lensfun - specifically to compile it. I have tried at various times since about 2008 to compile source code under Linux, without a single success, for a consistent set of reasons, primarily because the author of the source package always makes invalid assumptions about the environment in which I am requested to do this compiling. There is always some thing missing, so I no longer spend time on this activity; life is too short…
It maybe that I have to abandon my use of Darktable if I am unable to accept the level of distortion in this camera. Up to now, under Lightroom, this has not been an issue.