When I clicked on
recent questions feed on bottom of the site, I was navigated to the
/feeds endpoint; where I can see the code.
I don't know if this a bug, or does the page always show such code?
Yes, this is intentional. This is an Atom feed (also mistakenly called RSS feed - that's actually a different protocol, but it's using the same icon) and if you have an appropriate program/app (a so-called 'reader') it will organize all feeds you subscribe to (from Stack Exchange or other websites). If you don't have a reader, your browser will offer to download it or show it as 'code', because in essence it's 'just' an XML file (though it is a specialized version of XML).