I'm a little confused by this - are you referring to Chrome on MacOS and Windows...

frigid on June 7, 2020 | parent | context | favorite | on: Google Chromium, sans integration with Google

I'm a little confused by this - are you referring to Chrome on MacOS and Windows only allowing extensions from the Chrome Web Store? With all other versions of Chrome and Chromium, you can drag-and-drop compiled extensions by default.