It would appear that your LED operating at 600nm is at a slightly different wavelength from the DUKA which as I understand it is 598nm
I don't think that's a meaningful difference.
Did you run color tests with and without the Duka? Like I said, fog starts subtle. If it didn't bother you somehow, that's all the better.
If you had the same Durst light as I did then I agree it was as good as useless. I used the deep green filter that was for colour paper prints and after a full 15 mins I still couldn't see my hand waving in front of my face
Might have been the same, yeah. A filter like that is always, well, crap to put it simply. As you said, the device was useless. I no longer have it and I never actually used it beyond brief testing.
a general feeling that RA4 = total darkness we will always tend to suggest that total darkness is the only way to process colour paper
I'd gladly be proven different but the problem like you said is a lack of people who try it and if they do, the only thing they say is "I had no problem" without it even being clear if they actually tested anything or just printed away and didn't look for any issues. FYI that particular method worked OK for me for a few sessions with the LED safelight; everything seems nice and dandy until I actually scrutinized the prints and did some systematic side by side testing. Now my Ektar prints look like Ektar again instead of like Pro400H.