I know there are plenty of esoteric programming languages that are designed to be incredibly difficult to work with, like Malbolge, Brainfuck, and PikaLang, though programs written in them can still be compiled and run by a computer.

There are lots of constructed linguistic languages, like Esperanto and Toki Pona, but for most of those they are designed to be easier to learn or have other functional benefits. Are there any linguistic languages where the goal is to be difficult to speak, write, and understand, while still being actual languages?