New Samsung phones block sideloading by default

Technically, Android already blocks sideloading by default at an operating system level. The permission that’s needed to silently install new apps without prompting the user, INSTALL_PACKAGES, can only be granted to preinstalled app stores like the Google Play Store, and it’s granted automatically to apps that request it. The permission that most third-party app stores end up using, REQUEST_INSTALL_PACKAGES, has to be granted explicitly by the user. Even then, Android will prompt the user every time an app with this permission tries to install a new app.