Vivaldi has added ‘Load Animations’ section above the existing Load Images, which appears when you click ‘Toggle Images’ icon in the status bar. When you choose ‘Never’ for it, GIF animations will be disabled in the browser, this also applies for animations created from PNGs and SVGs also.

By default, Vivaldi browser always displays the GIF animations. When you choose ‘Once’, they’ll be loaded one time only. If you hide the status bar in Vivaldi, then no way you can deactivate the animations, as you know View menu only offers ‘load images’ toggle option but not load animations toggle option.

Note: The feature has been added by the Vivaldi team in Vivaldi 1.11 snapshot which you can download from here. 

Vivaldi 1.11 adds Configuration Panel for Reader Mode    

Vivaldi makes Alt+R as default Keyboard Shortcut for Reader Mode

If you want to disable animated GIFs in Chrome, Firefox and Internet Explorer browser, check the below link.

How to Disable Animated GIFs in Chrome, Firefox and Internet Explorer Browsers

This snapshot has also offers an option to “adjust the gesture sensitivity by setting the minimum stroke length required for the gesture to be registered.”