David, I haven't tried PureRAW, but from what I understand it is basically a stripped down version of PL4, which I use fairly frequently. And for what it's worth, on two different Windows 10 computers, I get PL4 to open and run DeepPrime on DNG files generated by LR all the time. I save out a new DNG file from PL4, and back in LR it acts just like any other RAW file, except that it now has the noise removed. The DeepPrime noise removal is generally supurb, though sometimes I get better results from Topaz Denoise AI if I play with its controls; it depends on the image. Either one is leaps and bounds ahead of LR for noise reduction.
My workflow is to convert RAW files to DNG upon import into LR. Then if I decide to use DeepPrime, that is the very first thing I do, by selecting File>Plug-in Extras>Transfer to DxO Photolab 4. Any changes you make in LR (including default settings, like sharpening & NR) will be ignored when it goes to PL4 (and, I assume, PureRAW). After running DeepPrime, I export to LR as a DNG file, which has the suffix _DxO added to the file name.
DeepPrime does use a lot of CPU or graphics card resources though, and I find it will occasionally fail if I have other programs running that compete for those resources. Try it with other programs closed, which sometimes cures a problem with DeepPrime failing. You mentioned that with PureRAW you are getting a graphics card error. Assuming PureRaw has similar settings as PL4, under Preferences>Performance>DeepPrime Acceleration, try changing the settings between Auto, CPU, and your graphics card, and see if it makes a difference.