On Android 14, Google started blocking old apps (those targeting a target API lower than 23, i.e. anything before Marshmallow/Android 6) from being installed.

While this behaviour can be overridden by calling adb install (respectively pm install if you've got access to a root shell on your device) with the --bypass-low-target-sdk-block flag, it still breaks simple manual installation of older APKs, as well as any backup apps and other software like that which hasn't yet been updated for this ne