I got some Flash applications[0] working in the Pro version of my remote, isolated iframe-embeddable multiplayer web browser[1] using Ruffle[2].
I use CRDP (chrome remote debugging protocol)[3] to run Ruffle on pages that need it (sort of like a Chrome extension content script). Ruffle itself uses wasm and is quite fast.
It's cool seeing the audio and video work and playing those old games.