Hi @khronoss! Welcome to the community! Please have a look at the introductory posts in the #start-here category if you haven’t had a chance to do so.
This not strictly answer to your question, this is more of an alternative approach.
I would strongly advise against installing flash player plugin and adding it to Firefox. It has many vulnerabilities and known to cause numerous issues with Firefox and with Linux in general. Moreover: it’s quite rarely used now, and for most mainstream sites you don’t need it anymore. I personally haven’t installed in on my Fedora system for three to four years at least, and I don’t feel the need to.
If you absolutely have to have it, I suggest installing Google Chrome in addition to Firefox. Google Chrome has built-in flash plugin which you don’t have to install, update etc. Then you can use Firefox for your general browsing (and know you’re as safe as you can be without known bad plugins polluting your browser), and then open sites you know you have to use flash for in Google Chrome.
You can install Google Chrome easily using these commands:
sudo dnf install fedora-workstation-repositories
sudo dnf check-update
sudo dnf install google-chrome-stable