Vivaldi 2.11.1811.33 is this year's first desktop update and comes with "a new and improved" Pop-out video mode, Themes update to match the OS dark/light mode, the ability to shift focus between different UI areas using the keyboard, upgraded developer tools, and improved full-screen tab casting.
https://www.notebookcheck.net/Vivaldi-2-11-now-available-with-improved-Pop-out-video-mode.453762.0.html