is there a way to learn Yiddish on duolingo?
Not to be a downer, but Yiddish has been in the incubator for over 3 years with little progress. Two years ago they set a completion date about two years in the future which has now come and gone without an update. When called out heavily in the forums around the same time, the team said they did most of their work offline and they do seem to have the tree already planned, but again, there's been very little progress since. There were requests to replace the team, which got ignored, so three native speakers on DL finally made a memrise course, which sounds pretty good: https://forum.duolingo.com/comment/18660169/Yiddish-course-is-here