Here's an api made by mprep [C# / .NET] Unofficial Bitcointalk API - Get info from boards, topics and posts
[1]. Feel free to check it.
I know the ninjastic.space website or tryninja or loycev make something like this as well.
I found the thread of tryninja about the api, kindly chrck here
[2]I know its not in rss or xml format but you can optimize it or use it to get the latest posts or every post made in this forum.
Edit: Here's a confirmed discord project that can fetch latest post of certain board made using tryninja's api tool
[3][1]
https://bitcointalk.org/index.php?topic1783893.0[2]
https://bitcointalk.org/index.php?topic=5273824.0[3]
https://bitcointalk.org/index.php?topic=5247383.msg58501819#msg58501819