Mainstream end of support for Windows 10 21H2 LTSC is 2027-01-12. But the process to switch is not particularly easy nor is it free. You need a Windows 10 LTSC license.
Windows 10 client LTSC is getting five years of support now, although IoT Enterprise LTSC is still getting 10 years of support. These changes do not affect previous LTSB/LTSC releases, including ...
We can expect that the next LTSC *after* Windows 10 Enterprise LTSC 2021 will be built ... we recommend moving to Windows 10 IoT LTSC. Microsoft recently revised the support timeframes for Windows ...