Can't play .swf file on Ubuntu 20.04.1

I created a .swf file and want to play it on my computer. At first, I realized I did not have Adobe Flash for Firefox, so I installed it this way. Then, I tried playing the .swf file again, and now the following message shows up

application/x-shockwave-flash decoder is required to play the file, but it is not installed

I looked it up on the Ubuntu Software center but could not find it. Could somebody tell me how to install it? Here is some info about my computer

EDIT: At first, I tried opening the file with the default video player on Ubuntu and this is what appears. Afterwards, I tried opening the file using Firefox and now this appears. Every time I click on "Ok" another tab is opened with the same message.

Solution 1:

Flash is deprecated technology and the (Shockwave) Flash decoder is no longer part of the Ubuntu Software Center. Please use the standalone Adobe Flash Player Projector available for download on Adobe's website here:

https://www.adobe.com/support/flashplayer/debug_downloads.html

The Linux version is in a nested archive, so you will need to click twice to get to the actual program.