Also, how accessible is this content from the perspective of a screen reader?
Apart from that with Threlte I personally practice documentation-driven-development, so ecosystem packages are exhaustively documented. If you're missing something, let us know via an issue[1] or on Discord[2].
Accessibility is a topic we didn't care enough yet to be perfectly honest. Accessibility doesn't stop at screen readers though, it's about contrast, size, colors, motion, reachability, and so much more that we cannot provide and are a consumer topic. Naturally WebGL apps suffer from being practically invisible to screenreaders. There are workarounds[3] but essentially this has to be solved by consumers of Threlte (devs) and hopefully by browser vendors at some point in the future.