I was able to use Ruffle and an old Flash game of mine (from 2010) on itch.io just now by packaging it as a .zip
The zip file contains:
- index.html
- This uses a simple <embed src="the-file.swf"> tag for the Flash .swf file itself
- It uses a script tag from https://ruffle.rs
- the swf
It used ActionScript 3 so Ruffle is giving an extra warning… but it works!