Microsoft states explicitly: "If you've deployed Microsoft 365 Apps for enterprise to the users in your organization, you don't need Office LTSC 2021. Microsoft 365 Apps for enterprise already has all the features that are included in Office LTSC 2021, along with many more features that aren't in Office LTSC 2021."
Once activated, the software does not require an ongoing internet connection, making it ideal for restricted or highly regulated environments. Core Differences: LTSC vs. Microsoft 365 Microsoft Office LTSC 2021 PRO PLUS 16.0.14332....
This version includes a subset of features that were previously exclusive to Microsoft 365: Microsoft Office LTSC 2021 PRO PLUS 16.0.14332....
: Advanced document creation with enhanced OpenDocument Format (ODF) 1.3 support. Microsoft Office LTSC 2021 PRO PLUS 16.0.14332....