Angle - Screen Rotation Orientation Lock Control is a free Android application that allows you to choose and lock your preferred screen orientation. This is achieved through a notification that is always up, allowing you to select portrait, upside down (if your device supports it), landscape, or landscape to the other side. The app also supports a dark mode that fits nicely with dark themes and actions for quick settings at the top.

It is important to note that if you have a phone, it is possible that rotation won't work on your homescreen (launcher), but it will work in apps. This is an open-source application, with code available on GitHub. The required permissions are WRITE_SETTINGS to change device orientation and RECEIVE_ON_BOOT_COMPLETE to launch notification on boot.