1. Vivaldi supports uBlock Origin, if you consider Firefox a "major browser" then sure also Vivaldi and Brave are major browsers

2. while I use uBlock Origin on phone (Firefox) and desktop (Vivaldi), it's overrated, AdGuard works under MV3 AND unlike uBlock supports element picker, so if I was on browser not supporting uBO I would switch to AdGuard since I can't live without element picker