Sideload apps not on App Store
From AppleGamingWiki, the wiki about gaming on M1 Apple silicon Macs
Sideloading history
Sideloading is last enabled in macOS 11.2. Sideloading was disabled in macOS 11.3 beta and in the current macOS 11.3 full release. If one attempts to sideload an app, the erorr message "This application cannot be installed because the developer did not intend for it to run on this platform" appears.