The Flash authoring tool comes bundled with a standalone Flash movie player that can open .swf files. It's available here, but I have no idea if this will continue to work (the page warns against using this if you're not a developer): https://www.adobe.com/support/flashplayer/debug_downloads.ht...

It's also possible to export any Flash movie as a standalone executable with the Flash runtime baked in. This should be immune to any sort of deprecation. Of course this relies on the developer who holds the original source file to do the exporting.