I have a similar question to @louisemcmahon
I can get the most recent posts from the API
/api/recent/posts(API route code
I can see that there is no way of getting all posts (at least I do not see it). Do you know if there is a workaround or there is a plan to add this feature?
it sounds like you want the contents of a topic client side to process.
if you have a browser that is ES6 compliant (chrome confirmed, firefox is probably good, not sure about safari, IE is out) then this GIST will work fr downloading a single topic as CSV.
to select the topic to download you edit the final line of that script to include the topic ID you wish to save, replacing the example topic id (in this case 20937) with the one you desire.
then execute the script in your browser console while being on the target forum.
if it complains about window.socket not existing on line 84 of the script, simply refresh the forum with the console open and try again. I've not figured out why, but sometimes chrome can't find the websocket object used by the forums if the console is opened after the page loads.