I never responded this thread because it involves things like “Unity”, “Gnome”, “colord”, and “Ubuntu 16.04”, plus monitor profiles made in Windows using proprietary software and flashed into the monitor chip. However, today I:
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Read through this thread and noticed the LAB LUT BenQ monitor profile
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Installed an ArgyllCMS LAB LUT monitor profile as my own system monitor profile and told Firefox to use this LUT profile, and similarly with GIMP
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Fired up Firefox and looked at some images in my online Gallery - the colors are horrible.
Having done the above, I can see some very clear reasons why @anon41087856 might have formed a very bad opinion of ICC profile color management.
Firefox hasn’t supported the use of LUT monitor profiles since Firefox V4, which was a long time ago. Back then Firefox used LCMS as the color management engine. LAB and XYZ LUT monitor profiles were supported. Black point compensation was supported. Photographers were happy.
Then a security alert was issued for LCMS and instead of waiting the short time for a fix (like Firefox never has its own security issues), Firefox decided to roll their own color management system, “qms”, and Firefox lost support for LUT monitor profiles and also for black point compensation.
According to this bug report filed 9 years ago, the lack of Firefox support for LUT profiles was “fixed” 6 years ago:
But the “fix” hasn’t yet been committed to Firefox code:
The last comment to the above bug report was three years ago. So it’s anyone’s guess if Firefox will ever support LAB LUT monitor profiles. As I recall, for XYZ LUT monitor profiles probably Firefox only used the embedded matrix if any instead of the actual LUTs, and if not uses sRGB. Leastways this is what Google Chrome does.
Which brings the topic around the problem of ICC profile implementation. Every OS and application seems to do their own thing, leaving users to deal with the resulting inconsistencies.
I’ve dealt with this issue of inconsistent implementations over the years, bit by bit, and never really stopped to think about all the things I’ve done to ensure that ICC profile “stuff” on my own computer produces consistent results across applications.
Anyway, some time tomorrow I’m planning to make a pixls post entitled something like “Comparing OCIO and ICC color management and implementation problems”, or “25 things I don’t like about ICC profile color management, that maybe OCIO does better”, or etc, unless perhaps @anon41087856 starts a similar thread first 
. It would be very nice for ICC profile users to have a working understanding of OCIO and vice versa, and I’m guessing there is less room in OCIO for variations in implementation.
In the meantime, @anon41087856 - did you ever manage to get darktable and your other softwares to display consistent results? If not, I think @gwgill might have insight into navigating some of the complications resulting from using colord and GNOME, but then again your version of Ubuntu might still use Mir, that might complicate things.
That huge LAB LUT BenQ profile provides all six AtoB/BtoA tags. My own ArgyllCMS LAB LUT profile only has a single AtoB0 tag, for relative colorimetric intent, which somewhat reduces the possibilities for “different results on different softwares and operating systems”.
Apart from affecting the black point, and depending on the conversion intent and whether black point compensation is used (implementation of both of these vary from one ICC profile application and CMM to the next) that BenQ LAB LUT profile does seem very close to AdobeRGB1998. But I say this based only on looking at a couple of images and converting to the LUT profile and then assigning AdobeRGB1998. I haven’t taken the time to use ArgyllCMS command line utilities to plot the respective color gamuts and TRCs of AdobeRGB1998 and the BenQ LAB LUT profile.
