I reckon it'll be possible to "simplify" it even more for an end-user, by making a static site generator generate these redirect HTML files from markdown or a CSV.
Some guy shared his project in this post that does exactly that! Yes while that is possible and can get to a high level of automation via GitHub actions, the point of my URL shortener was more of people could post a link easily with a simple interface (like the interface for adding a new issue). But if I were operating with a fixed set of short links, then this would have been a good method!
<meta http-equiv="refresh" content="1; url='https://news.ycombinator.com/'" />
in the header.