LLMs like ChatGPT don't crawl your entire site, but in theory they can crawl anything guests can view with the right prompt. llms.txt is a new, experimental standard some sites are starting to publish to declare their rules for large language models, but it has not been adopted yet. For now, the best thing you can do is run a test to make sure ChatGPT can crawl your URL and it's not being blocked by something like Cloudflare. Because ChatGPT would probably ignore the replies from forum posts, one work-around might be to use wget to download the pages and then upload the HTML files to ChatGPT allowing you to fully scan them.