Richard Farwell1 wrote:
I think Mojave was the last 32-bit system and when they went to 64-bit Catalina they dropped all apps that were 32-bit and the developers had too. Apple had never wanted to upgrade QuickTime 7 Pro to 64-bit. So those who still use QuickTime 7 pro Mojave is our only option.
Yes that is correct for QuickTime 7 Pro.
If you replace that Mac mini with a newer Mac mini, QuickTime Player is still in all of the later macOS versions.
If you need something different, then maybe try VLC http://www.videolan.org/vlc/
For others, see > https://mac.eltima.com/quicktime-alternative-mac.html
If you need editing software, then iMovie, Filmora, DaVinci Resolve and Final Cut Pro come to mind.