As I pick up this discussion -- I have had the same type of problem related to exporting discussion board posts -- it seems that several "solutions" have been offered, but that they may not be exactly what some people are looking for. In that spirit, I'll offer a "solution" that I use, which also has some limitations. Here's my approach:
1. I use the Chrome plug-in GoFullPage to capture the full discussion board that is displayed on my laptop, taking care to "Expand Threads." This provides a nice pdf document that captures the entire discussion board displayed before you. If the discussion is particularly lengthy, then the software may spilt it into a couple pdfs.
2. You can then print out the pdf or upload it into other applications -- maybe there are applications available online that can convert a pdf to a file that is more easily editable or that you can cut, copy, or paste.
3. I myself attach the pdf of the discussion board to an AI platform, Perplexity is what I currently prefer, and find that I can coax a nice summary of the discussion or a punchy recap of the discussion flow. Going forward, I may ask it to evaluate the quality of particular student posts. But I have also discovered -- at least in my limited trial-and-error experimentation -- that ChatGPT could not read or extract the discussion from the pdf that GoFullPage exported.
4. BTW in my experience the pdfs exported by GoFullPage can be quite large (e.g., 24MB).
I hope this is helpful to some of those with this issue.