[zacte]

Are there any decent alternatives for the Chrome Web store? Are there unified extension hubs for chromium/firefox with version history similar to how android has apk websites

[YoshiRulz]

Mozilla's first-party marketplace has version history. Click "See all versions" in the left sidebar.

As for third-party marketplaces, I couldn't say, but I'm aware of some work in that direction for Nixpkgs.