Are you using a custom domain url to test it, or the glideapp url? When you installed it on your device, what url did you use? That’s a browser message and should be showing due to the URL you used.
Your app will use the URL you’re viewing it at. Even Pro apps can still be viewed at their glideapp.io/play/ABC123 link, which will display glideapp.io/play/ABC123 as their URL. Make sure you only use your custom link, and that’s all users will see.