I was on r/duolingo and I saw a post from u/rebane2001 who made a back up of the entire forum. Yes, the whole thing... every discussion, every subforum. Here's the link: https://duolingo.hobune.stream/
Here's the post on reddit:
The archive contains nearly every forum thread where the ID ranges from 0 to 1400000, or from 46800000 to 57005930. In addition to that, nearly every post showing up in the "top posts of all time" section is also available in this archive, filling most of the missing threads in the 1400000 to 46800000 ID gap. Note that the IDs don't represent the amount of forum threads, as every reply to a thread also incremented the ID.
There are a total of 2098402 forum threads in this archive.
This is incredible! A million thanks to rebane2001, whoever you are, and wherever you are, bless your soul.