Will this affect alternative app stores like F-droid or is it only about downloading and installing an APK with a web browser?
An example of "normal" users that side load (through F-droid or direct APK) is most Ingress players. While Ingress itself is in the playstore most people use the "companion" intel app called IITC which isn't in the playstore as it's technically against the ToS.
An example of "normal" users that side load (through F-droid or direct APK) is most Ingress players. While Ingress itself is in the playstore most people use the "companion" intel app called IITC which isn't in the playstore as it's technically against the ToS.