+1, though Testflight supports MacOS now, it would be better if we can just sign and install Safari webext locally. Safari WebExt is not a typical MacOS app, it is closely coupled with browser. It seems none of the popular test automation framework has the privilege to config the Mac privacy settings and "allow unsigned extension" in Safari developers settings Compared with for Chromium, Firefox, the test automation is straightforward, this limitation brings a lot of difficulties to the e2e testing.

Found the solution, this API will resolve: https://developer.apple.com/documentation/safariservices/sfsafariapplication/2202266-showpreferencesforextension.