That’s as far down the chain as I went too (linked in my post above). I might go back to cudaPackages in a few weeks and have a dig if I get time. I was meandering through there late last night (and cudaPackages11 to see if an older version of the drivers and CUDA would suit the card better).
With your mention of 12GB and 2 cards, I tried to slip a spare 4GB GTX1050Ti into the machine just to see if I could get it going. I couldn’t get Debian to see both cards, and I had the same issue with NixOS. I suspect it’s probably a hardware issue (limited PCIe lanes or some such) rather than a Linux issue.
Next step will be to take my shiny new configuration.nix and drop the GTX1050Ti into another machine I have here, feed it the config, and see NixOS work its magic to deliver me a working system. I might give that a go next week if I have time. It’d be a good way to test out the whole essence of NixOS → insert configuration → receive reproducible build.
(Edit: actually, I’ve got some free time now. I’ll drop the configuration.nix into the Z220 + GTX1050Ti setup mentioned in my initial post and see what happens. Will post the results into the NixOS thread as that’s where it’ll be more relevant.)