`mo.mpl.interactive()`

yes they currently don't support it, as far as i know. you can check out their supported interactive backends: https://matplotlib.org/stable/users/explain/figure/backends.html#interactive-backends

we use WebAgg ourselves

this WebAgg renders the plot as a raster image, correct?

Not exactly sure. But it connects via a websocket (maybe more ways to connect) which is difficult to pull off in wasm