Step-by-step instructions to get AnimateGif working on Monterey:
Download AnimatedGif.saver.zip
Double-click AnimatedGif.saver.zip to uncompress it to AnimatedGif.saver
Double-click AnimatedGif.saver to install it
Install it "for this user only"
Wait until the System Preferences > Desktop & Screen Saver opens by itself
Choose AnimatedGif screen saver
Click "Screen Saver Options…"
Choose a Gif >> THAT IS IN THE PICTURES FOLDER! << You can change that later.
Click on "Preview" when hovering over the preview window
Wait for the dialog that "AnimatedGif.saver can't be opened..."
Click on "Show in Finder"
Wait for the Finder window to open
Right-click the AnimatedGif.saver file and choose "Open".
Nothing happens. This is by design.
Change back to the System Preferences > Desktop & Screen Saver dialog
Switch to any other screen saver, then back to AnimatedGif
Click on "Preview" when hovering over the preview window
Wait for the dialog that "AnimatedGif.saver can't be opened..."
Click on "Open"
Now the screen saver chosen starts. And will so in the future, without any dialog.
Why all this?
Unknown binaries are not executed by default without valid (or no) certificate. The "right-click and choose open" is a way to tell macOS that you don't care for validation, and it will remember that choice, once made.
Step-by-step instructions to get AnimateGif working on Monterey:
Why all this? Unknown binaries are not executed by default without valid (or no) certificate. The "right-click and choose open" is a way to tell macOS that you don't care for validation, and it will remember that choice, once made.