https://github.com/kiwibrowser/src.next

"Important note: Kiwi Browser is now archived. It will no longer be maintained after January 2025.

The extensions code for Kiwi Browser has now been integrated into Microsoft Edge Canary.

To install extensions on Microsoft Edge Canary:

Open Microsoft Edge Canary and go to Settings > About Microsoft Edge.
Tap the Edge build number (e.g., ) 5 times to enable Developer Options.xx.0.2487.0
In Developer Options, select Extension install by id.
To find the extension ID:

Open the Microsoft Edge Web Store.
Locate and select the desired extension.
Copy the ID from the URL (e.g., for Bitwarden, the ID is from the URL ending).jbkfoedolllekgbhcbcoahefnbanhhlh
Paste the extension ID into the Extension install by id field.
The extension will install.
If you really need Kiwi Browser, you can download the latest published version of Kiwi Browser here. Do not download Kiwi Browser from any other sources.

While your Kiwi Browser installation will still work for some time, it’s essential to explore alternatives like Microsoft Edge Canary, Vivaldi Browser or Mozilla Firefox to stay secure and up-to-date.

-- Arnaud."

Kiwi 浏览器的扩展代码已经集成到 Microsoft Edge Canary 中，我已经用了好几天了。