It is clear to me that TIFF files are different than camera RAW files. But 48 bit TIFF files basically contain similar information. It probably wouldn’t take much effort to convert them to linear DNG. So you could also use PureRAW to enhance scanned images. It would be a useful extension, right?
It is not a question of whether TIFF files contain similar information. DeepPRIME and DeepPRIME XD both are applied to output files as part of raw file demosaicing. Since TIFF files are already demosaiced DeepPRIME and DeepPRIME XD can not be applied to them.
Neither will PR work on linear DNGs.