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
cd1e0328df0266da5c9ae8aa8f1a7931252f6610f773ba7c2ecae3ad1a72b0f5.
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.