hi so i just checked the osrs page and looked at osrs mobile and i read this :
Only supported Android devices can download the application: all devices with Android Lollipop (5.0) or later.
EXCEPT for: all Chromebooks, ASUS Nexus 7, HTX Nexus 9, NVIDIA Shield, Google Pixel C, and Huawei P8 Lite. There are issues with the performance of Old School RuneScape on these devices.
so the weird thing is i have a huawei p8 lite and i was able to download the osrs mobile app