I use Vivaldi (EU), it has an inbuild adblocker. In chromium browsers Mv3 means that Mv2 Extensions are eliminated from the Chrome Store in June this Year. Mv3 adblockers are still there, there is uBO light (same as uBO, but without element picker) and Adblock Plus, which is pretty equivalent to uBO. The inbuild ad/trackerblocker (customizable with own filterlists or those from uBO, DDG, AdBlock plus and others) in Vivaldi isn't affected by Mv3 and pretty effective (>99% in the test). In extensions other than those related to security and privacy, it's irrelevant for the user if they are Mv2 or Mv3 and mostly redundant in Vivaldi.

If you prefer Gecko browsers, the only one from the EU is the Mullvad Browser (Sweden), which can still use uBO, but also Gecko Browser will not support Mv2 all eternity because the related different cookie management used by most webpages with Google APIs, also apart from the will of the devs to continue developing MV2 for a minority engine, such as Gecko (~ 4% Market Share).