Btw /agatha2/index.rss is broken. There is an XML parsing error due to & in the title. It should be replaced with &amp . Other boards like /news/ have the same problem, while those not having & have a functioning index.rss, like /operate/index.rss or /polru/index.rss .
You can check if an RSS feed is valid with an RSS feed validator like https://validator.w3.org/feed .