There's no app yet, but there is a Progressive Web App (PWA) which is like a website in its own app. If you use Chrome, you can get the PWA by going to kbin's front page, open Chrome's three dot menu, then press "Add to Home screen."
Are you using a VPN like Adguard? I also had that problem and disabling it temporarily allowed me to install the PWA properly instead of a home screen short cut.
That's wierd. If auto ration is disabled at the Android system level I don't think it's possible for an app or a web page to overide that. Are you sure auto rotation is off in Settings or Quick settings?
Most androids allow you to lock auto rotation from the swipe down menu. Have a look at your quick menu above your notifications. If it's not there, look for an edit quick menu button nearby, and you should be able to add a lock orientation button to your quick menu manually. If you can't find that, check the app Store for a forced override app that adds the feature for you.
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