Microsoft has slightly changed the name of the new Office LTSC product, perhaps as a clue to their future intentions for the Long-Term Servicing Channel product line.
LTSC stands for Long Term Servicing Channel see The good and bad in Office LTSC
Office LTSC is now Office LTSC 2021
Only now Microsoft has changed from Office LTSC to Office LTSC 2021 for example “Office LTSC Professional Plus 2021”
No explanation for the change, it just appeared on the Microsoft product pages.
It suggests that Microsoft is planning future Office LTSC releases.
There’s also a Windows LTSC product line.