The .zip-file that contains the offline version of kn Secrets can be downloaded here.
To verify that the .zip-file is genuine, use any appropriate tool to compute its SHA256 hash value. The SHA256 hash value should come out to be
07973a02f6c27d649dad0d0f330e5800492112476364d73108d0c4face76ff3d.
Once successfully verified, unzip the file into a directory on your disk, find the file "index.html" in that directory, and double-click that file to start kn Secrets in offline mode. Please follow the security guidelines whenever using kn Secrets in offline mode.