There is a way to make this work. With ExifTool it’s possible to change the creator software and metadata of an image to trick PhotoLab into thinking the image is on the allowed list – ExifTool could be scripted. I was able to do this to test iPhone 11 RAW images (which turned out great) by changing the metadata to iPhone X. With my current iPhone 13 Pro, there’s no point as the images are no longer supported.
Since you have linear DNG the format should be standard. The trick here would be to use MetaImage to change the metadata to an acceptable camera, i.e. PhotoLab Linear DNG.
I’d love to know how it goes, as would @Stenis so please report the results.