I don't think your assessment of the DJI Mini thing is very fair. Sounds like they would be more than happy to accept a pull request and indeed there is an open one the maintainers are helping get merged [1].
Shame that the new workflow doesn't work well for your particular camera and setup - but I would encourage other people to try it, because it works great for mine.
We know :-) It very much seems there is no dt developer currently interested in this sort of correction, i suppose none are using such devices.
Just two reminders:
Such "missing support for my camera" started me to get into darktable code. A lot of code to be reused is there, there are already some hints, just go ahead :-)
Some comments above i suggested something ... :-)
Shame that the new workflow doesn't work well for your particular camera and setup - but I would encourage other people to try it, because it works great for mine.
1: https://github.com/darktable-org/darktable/pull/20467