List all installed macOS packages
"brew List" will give you a list of packages installed by Homebrew and "port installed" will do the same for MacPorts. I don't know a similar command for Fink but it should be listed in the Fink User's Guide.

To get a more general list of installed software, go to "About This Mac" found under the Apple menu. There are two buttons on the image that pops up. Select "System Reports". This opens a window which lists about everything for your Mac. On the left side of the window, about two-thirds of the way down is the word Software. Click on this and just explore. It will tell you much about the installed software.