The only feature i miss on Opera is an: Tab Split Screen !
Arc Browser do it
Vivaldi do it
Microsoft Edge will do it : https://mspoweruser.com/microsoft-is-testing-a-new-split-screen-feature-for-edge-browser/
Lot of users ask for it :
We currently have wide screens, and it's currently boring to always switch tab or always rearrange windows, and we no need an opera sidebar on each manually splits that we tinker with Windows, etc...
I like opera, but i'm near to leave it because there is not this basic function.