As it is announced years ago the Flash Player is going away. https://www.adobe.com/products/flashplayer/end-of-life.html
However there are Flash apps that are not going away and even the end users don't use it, there is a value running them to see how the legacy systems worked.
So my question: is there a virtual machine image or container where we can still run flash players with the older versions of browsers and extensions? I see people are trying this approach but could not find a community effort.
Yes, there are virtual images that can do this.
Let me list all steps, total process takes around 15 mins (assuming you have a high speed connection)
I explained for virtual box but it is also doable for VMware.
1 - Go to https://www.virtualbox.org/wiki/Downloads and download and install Virtual Box
2 - Go to https://www.osboxes.org/linux-lite/#linux-lite-4-vbox and download and unzip Linux Lite 4.0 (Beware it is a 1.3GB download!!)
If you want VMware you can download VMware image too.
I tried with Linux Lite 4.6, it also works but don't use a higher version, they won't work.
3 - Create a new virtual machine (Linux, 64 bit) and select Linux Lite 4.0 (64bit).vdi as the "existing virtual harddisk file"
4 - Start the machine.
Username: osboxes Password: osboxes.org
5 - Login, go to the Menu, hover over "Settings", and then open "Time and Date"
6 - "Unlock" and set the "Configuration" as "Manual". Then select a date before Jan 12, 2021. ( It may sync the time to normal again, if so unselect-select Manual again and now it will keep the time as what you set)
7 - Open Firefox, and go to your flash site such as : http://www.sfskids.org/play/
8 - Voilà! Music is there! and so your flash.