For Office 2021, Microsoft does not provide a standalone "offline installer" file for proofing tools as it did for older versions like Office 2016 . Instead, you must Office Deployment Tool (ODT) to download and package the language files for offline use Method 1: Using the Office Deployment Tool (Recommended)

Q3: Does this work with Office LTSC 2021?

Final Recommendation

Have you deployed offline proofing languages in your org? Let me know your deployment script in the comments below.

: This file is a "stub" installer; it will still require an active internet connection during the actual installation process to fetch the full proofing tool data. Option 3: Third-Party Utility (Office Tool Plus)

Note:

If you are an IT administrator managing volume licensed versions (LTSC), you should download these through the Volume Licensing Service Center (VLSC) .

Installing Proofing Tools...

For enterprise environments, the offline installer is clearly superior.