The Language Hunters site has a temporary tutorial in Gaeilge (Irish), and I’ve tried to copy along with it. What I found is that a) it is quite different from most other European languages I’ve tried, b) still some Indo-European is immediately noticeable, and that c) it’s much harder to play when the other side is a video. The most exhausting aspect was the speed of the course, where one has to re-watch a video many times until fluent enough to proceed. That’s not necessarily bad, but different from “real” play. Also, the language did not stick nearly as much as in a real-life game. But these videos are quite good for getting to know the game itself, and, as with any martial art, can be only a kick-off for practicing in many real circumstances.
I only did it up to video 15, then got distracted, and will see how easy it is to re-enter after a month-long pause soon :)