Apparently adding <link rel="stylesheet" ... in the document body is considered a bad practice by W3C standards. The same for adding <style> blocks in the body…
So are there any standard-compliant solutions to add CSS outside of the <head> tag? Like at the end of the document.
If you only want to include your CSS styles on a specific events, there’s nothing stopping you from doing so at the head:
This has the added benefit of adding your stylesheet in an async way, which doesn’t block the browser from downloading anything else.