Time to wake this topic from hibernation.
After an intermediate quick test from a live system looked promising I kept the card but had to postpone any further investigations to “later”.
Fresh system (Bunsenlabs Boron) installed and the Nvidia driver installed, too.
Well, after I installed it and purged the install once before.
By now I am used to “edgy” technology not working in a reliable way.
For reference here is the apt command that pulls all the required dependencies - which seems to work because my card (GT1030) is supported by the default nvidia-driver package in debian.
_$ sudo apt install nvidia-opencl-icd
clinfo finds the card, darktable-cltest finds the card.
So … all is good?
Not quite yet. Time for another topic: