Sorry, you’re well out of the loop on this one, boss. Sideloading has been common practice for thousands? millions? of users since the beginning of android. There are plenty of apps not listed on Google Play - the ones that come top mind are Fortnight for a time and now the Epic Games Store app, and some VPN apps that couldn’t offer features like ad/malware blocking in their Play store versions. Sideloading means downloading an executable install file (an .APK file in this case) rather than installing from Google Play. And they are SEVERELY limiting this ability next year.