To set the window rule v2, we can use class, to get the class of applications that are running we can use:
hyprctl clients
We can use a class with regex also, or use the exact class name using the above command:
Window Rule V1:
windowrule = workspace 2, ^(.*Brave.*)$
Window Rule V2:
windowrulev2 = opacity 0.8 0.8,class:^(.*Brave.*)$
The second param is the class of brave browser or we can use the application title, as the second param instead:
Window Rule V1:
windowrule = workspace 2, ^(.*Brave.*)$,title:^(.*Brave.*)$
Window Rule V2:
windowrulev2 = opacity 0.8 0.8,class:^(.*Brave.*)$,title:^(.*Brave.*)$