Same here. I have so much great AS3 code that I can't even run for myself anymore. I used to run my own billing app that I wrote in AS3 for generating highly custom invoice templates. Even after I shut it down I still used it locally until Adobe destroyed Flash Player.
There was a pretty simple way to build a chromium based app with electron that allows you to run old flash application. I built this a few years ago for some customers in my old company because we had a flash backend which we couldn't port to js with reasonable effort.
A quick Google research shows that chromium disabled flash a while ago but you should still be able to use an older version in electron projects. Didn't test it but could be worth a shot.