So, as I wrote before, MS broke LibreOffice work (and just broke many Windows 10 system) with its stupid update KB5000802.
OK, they gave us the fix for that problem. But it will be optional (!!!!). You should install it manually if you have the problem!
For Windows 10 20H2 and Windows 10 (2004) install KB5001567,
For Windows 10 (1909) — KB5001566,
For Windows 10 (1809) — KB5001568
For Windows 10 (1803) — KB5001565.
Why they made it different for different builds of ONE OS Windows 10, I don't know. And I think they don't know too.
You can find your Windows 10 build number in system options - system - about (I can show you only Russian variant):