That's a consequence of its main flaw, which is that it's stuck for now in the 1990's and can only work on 8 bit RGB. They are working on a major change to the engine to address this, but IMHO it doesn't look like it's going to happen anytime soon. They have set the bar way too high.
You can however use the color menu anyway. You might just lose some dynamic if you edit things a lot, but that should be ok.
Or you can use Krita, KDE's answer to Gimp, which is nowhere near comparable in terms of reliability, UI and tools, but does handle Lab buffers, as well as 16 bit fixed or 32 bit floating point per component RGB.

A 'centrist' is someone who's neither on the left, nor on the left.