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Edge is now based on Chromium [1]. Welcome to the future, where you can choose from Chrome (Chromium), Edge (Chromium) and Opera (also Chromium).

do all of them use google extension store to install adblockers like Brave (also Chromium)?

They have their own stores apparently (at least the user-facing front).

Brave's shields are built-in, no extension from the Chrome Web Store is involved.