You're being modest. This is easily the most performant option... although it means losing interactivity (right clicking equations on GitHub allows copy to clipboard, A11y features, etc).
Running the JS client side, like GitHub, means blocking the thread. You're either going to be 1. delaying other JS from running, or 2. rendering late, shifting the layout – which is what GitHub has chosen: https://imgur.com/a/y47haf9
(Sending the rendered div's is a non-starter. Large document sizes delay domContentLoaded, slow down browsers, aren't shared cacheable resources, etc.)
Your approach, then. On your page there are 178 SVGs. Total gzipped size is 490KB. SVGO[0] gets that down to 311KB – that's 1.74KB transferred per equation. These are non-blocking, immutable, cacheable assets. Brilliant.
Upgrades:
- Figure out viewbox and inline height/width values on the HTML so no layout jank (aka "Cumulative Layout Shift"/CLS) occurs. Unsure if this is possible for inline math.
- Add `loading="lazy"` afterwards. Users that don't scroll the entire length of the page won't suffer unneeded downloads, and the inlined sizes will prevent late CLS for those that do.
- Maybe re-add interactivity? Cheap option: just support copying alt-text in a context menu.
[0] https://github.com/svg/svgo