when in the initializing screen, i see some long auth_callback url (tested with opera browser)
i never get the user/password fields, just stuck
no errors or warning in logs
if you had to install android system webview, then most likely your device is not using that by default. I do not think Android 5 devices allow changing the default webview package. If you have a custom ROM I think there is an exposed module that lets you set it, but you are kinda on your own here.
if you dont know what rooting, custom ROMs and xposed are then this may not work for you, its a pretty advanced android topic. Your device may not ship with compatible webview unfortunately.
Edit: android system webview is meant to be a system installed app, meaning if you had to manually install it then android will not use it by default. The xposed module makes it a system installed app so it can be used.