Let me take this opportunity to link again to the modular forms database: https://www.lmfdb.org/
Firefox for Android.
When it doesn’t work, is when column width is too wide to fit on a vertical screen at once, which isn’t a problem here when zoomed in.
It doesn't need to go to the opposite extreme (as you described it :-)) to be more readable by default on different screen sizes.
Regarding content, it started as a database of modular forms, indexed by various specialized numerical data; since then, it has grown to a repository of all kinds of number theoretic data, including number/function fields, elliptic curves, various special functions and much more.