...Sometimes, there is no results (chatbots) to return and the page shows 'Found 0 bots' message. Those pages exist in the sitemap and indexed but Google treats them as soft 404 and 404....In future such pages might have content...
Right now, you're fooling google because your site is mainly dynamic and it sounds to me that you want new users to become introduced to your site.
What I would suggest is to make the chat section more like a supplementary section accessible from the introductory page. Make the introductory page your home page that gives a perfect explanation of what your website is about using well-written paragraphs.
As for those chat pages, it is safe to indicate they should not be indexed because a) you're telling googlebot that you don't want to play tricks with it, and b) you're then delivering content (aka perfect paragraphs) on the main page that people want to see, and you want the main page to be indexed by google.