There have been a lot of recent stories about Google restricting sideloading to apps from developers who have registered with Google. Google has issued the very important clarification that adb will still be able to used to sideload unverified apps: https://support.google.com/android-developer-console/answer/16561738 [google.com]
So, if you own your phone, you can still install whatever you want on it. You just might have to install adb and enable the Developer Options menu first.