Diving into history, creating a mobile version was impossible in the earliest versions of CSS. Viewport units were amended only in 2012 with the introduction of CSS3. Prior to that, the only way to create a mobile version was to check the UA and, if it was a mobile device, redirect to a specific HTML page that was adapted for mobile devices. Probably, we will do this in the same way.
It's really easy, just make a Next.js site that uses jQuery to iframe a WASM VM running Docker to embed https://oldweb.today and use that to run Netscape Navigator and then screen capture it and send it to a LLM for it to generate an appropriate background track and have it email the user with a magnet link where they can torrent the mp3 to play next to the page. What could be simpler?