> Regular GAC 21H2 will last you only until June 13, 2023.

I got that date from the retirement date for Windows 10 Home and Pro at https://docs.microsoft.com/en-us/lifecycle/products/windows-...

So maybe 21H2 will be supported until Jun 13, 2023 but there will be newer feature updates for Windows 10 which will be supported until October 14th, 2025.