This is a large and steady market. Strange that DxO is cutting themselves out of it. Same issue with not supporting iPhone and Android DNG. PhotoLab does a great job with iPhone/Android DNG. There’s no good reason to cut themselves out of the mix.
Supporting linear TIFF inside DNG is a relatively easy task. Sure, some of the advanced lens correction may not work (most of it should, except out of DxO pedantry). The noise correction could be a little weaker. But DxO should make a best effort here.
If DxO is worried about giving the wrong impression (“not high enough quality”), sure show a warning about limitations every time one opens one of these only “partially supported” files. But DxO should surely give PhotoLab users best effort.
I’m expert enough in PhotoLab now, that it makes me really cross every time DxO forces me to use another tool.
Giving up an entry point into all the museums in the world seems strange. On the other hand, an entry point may not be enough. Enticing these museums to abandon Adobe would be an uphill battle. Those museums who care enough about software freedom to leave Adobe behind, are probably on Linux and using FOSS tools. Those FOSS tools are ugly and awkward but damn powerful at this point. There’s GIMP, DarkTable and RawTherapee which can all produce first class results in expert hands (not mine!).