However, they still need to distribute different packages, at least for the time being. But I can see a hypothetical unified store just letting you pick between the “Mozilla” or “Chromium” versions of extensions (perhaps automatically, based on your browser).
Problem with that is Firefox and Chrome (for example) aren’t the same browser under the hood and need different extension code to function
You couldn’t just use the Mozilla download of UBlock on Chrome, it’d have to be the Chrome addon served through Mozilla servers
Think of it like a phone economy: you can only install apps (extensions/add-ons) for your device (browser)
The chromium ones could all just use a single repository though I’m P sure, that’d work fine
Actually, modern extensions are rather similar between browsers, thanks to the WebExtensions API that was created a while ago. Mozilla even has a porting guide and list of differences: https://extensionworkshop.com/documentation/develop/porting-a-google-chrome-extension/
However, they still need to distribute different packages, at least for the time being. But I can see a hypothetical unified store just letting you pick between the “Mozilla” or “Chromium” versions of extensions (perhaps automatically, based on your browser).