Puzzling, since Wikipedia tells me, "Adobe
's DNG SDK
provides a software library for encoding and decoding lossless JPEG with up to 16 bits per sample."
As I said in my initial reply, whilst JPEG-LS is used as part of the DNG and DICOM standards, it is rarely found as a standalone format, and I am fairly certain that Lightroom Classic will not accept a JPEG-LS file. Victoria's idea of asking for a sample file seems sensible.
There is scanner software out that can generate DNG files - VueScan
certainly can. I have one of the legacy VueScan Professional licences with perpetual updates - newly bought licences only have a year of updates included. I have no idea what software the scanning bureau might use; it may well be something proprietary from their scanner vendor.
My family planned to send our slides out to a scanning service until a recent count discovered that there are around a thousand, almost all Kodachrome. At that point, the plan changed to buying a used Nikon Coolscan with the slide feeder attachment. I figure that I can buy a scanner, run these slides through and sell the equipment again once I've finished scanning for much cheaper overall than paying a service to scan that number of slides for me. I can always use VueScan to bulk scan the images and then adjust the scans later on. Note that if you're looking at used Nikons, you really need the SF-210 slide feeder if you have slides in cardboard mounts, such as the Kodachrome slides I need to scan - the earlier SF-200 is known to jam with cardboard mounts or if the slides are in variable thickness mounts. A high-end scanner is probably overkill from a resolution point of view, as these slides were almost all shot on cheap lenses by people of modest skill, but there's no way I'm tackling a thousand slides without a decent feeder!
I really need to see what negatives we have lying around, too - as it might be better to try to scan those with an appropriate Nikon attachment than to scan the prints. I know my parents were not that diligent in filing negatives, as they rarely had anything reprinted.