Having watched @s7habo most recent episode, I thought to try using paletton myself. I immediately came up against entering the base RGB - Palleton wants it in hex, but darktable’s color picker only seems to give RGB colours in decimal. I resorted to using a calculator to convert each coordinate one-by-one. It works, but is painfully slow.
I ran into that in the past and go to the Converting Colours website when I need a conversion. Precede the value with the format shown in the list. For example: RGB(80,54,36).
It accepts just about any format and translates to any other format.
Still a bit of a hassle but better then calculating them (which isn’t always that easy. try going from RGB to HSL).
darktable’s color picker is one of the modules that could benefit from an overhaul in my opinion.