I'd really like to make fuller use of Kstars and Ekos with my D7500 but for the last week I have been reverting to using a intervalometer for reliability. The primary issue has been lack of recording RAW NEF files when capturing, however after some experimentaiton I have got to a point where I am willing to give it another go again.

I am using GPhoto CCD (indi_nikon_ccd) Driver 2.9 interface 10. Under Image Settings I have a number of capture formats presented randing from the expected combinations of various JPEG qualities and RAW plus combinations of JPEG & RAW. There are also several "Unknown value" options which I decided to experiment with.
There are a number of issues however.
The standard JPEG options (Basic, Normal, Fine) work as advertised
The combinations of NEF+Basic/Normal/Fine do not work (error report "format is not supported")
NEF (Raw) format only produces JPEG images for some reason!
However, the 'unknown values' do produce NEF files, but with a JPEG file too, thus:

Unknown value 008 = RAW + Basic
Unknown value 009 = RAW + Basic*
Unknown value 00a = RAW + Normal
Unknown value 00b = RAW + Normal*
Unknown value 00c = RAW + Fine
Unknown value 00d = RAW + Fine*

So I have settled on '008' as I want the Raw file and do not care for the JPEG. I'll test how well this works later this evening!

The Issue with Kstars/Ekos however is that with these settings it does not download the Raw file every time (this is how it works for all of the unknown value modes I tested)

With Ekos in the CCD tab, Format set to Native - take an exposure and the result is a JPEG downloaded, the subsequent exposure is a NEF(Raw) download, next exposure is JPEG, next exposure is NEF and so it repeats...
With Ekos in the CCD tab, Format set to FITS - the result is a similar pattern with the resultant FITS file downloaded matching the JPEG bit rate then the NEF bit rate, and so it repeats...

This behaviour makes the local download and storage of the files a problem as every other one is the wanted raw file, the JPEG is of course no use other than to confirm I'm still on target.

It would be good if this worked reliably, happy to help out debugging if you let me know what is required to do so. (I tried enabling the debug in the options tab of the indi DSLR tab but it just flips back to disable!)

IIRC, issue with Nikon is resolved with updated libgphoto2.. where are you getting your INDI Library from? If it's from PPA, then it should be OK. Make sure the format is NOT NEF+JPEG as that is not supported. Just select NEF.

Ah the NEF+JPEG explains the same alternating between raw and jpg on the plate solve using the DSLR as well I've noticed tonight. I'll check the source of indi, I recall it compiled from the github but the libgphoto might be from the rasbpian repository. Is there an easy way to confirm library version?