I have the same issue, and i'm also on a Huawei device.
The qr-code never gets recognised.
It seems that are two possible login screens when you select sync by other options --> sign in. Most often it takes me to the homepage but then i get a very quick message saying the servers are down at the moment from the device.
Seldom does it takes me to a login screen on the device/app. that login-screen has the same theme as to whatever it is set, in my case Darkmode-Orange.
Every time i log in i get a mail and i hear a Ding on my phone, desktop and tablet.
One time i got prompted to login again to sync but after i did that it was like i logged out, 'cause it was back to square one. To try to sync again.
I've tried to do this for 2-3 times now always with days in between but it don't work. and for me to start using opera on other devices i need my passwords synced.
Plz dont ask me for screenshots i'll prolly wont provide. /regards F