I’ve double-checked because I’m not familiar with Microsoft licensing terminology. The extended support end period listed is included without extra cost, it’s just limited to security updates only. This is separate from “Extended Security Updates” which is paid for security updates after the support period has ended.

“The Extended Support phase follows Mainstream Support. At the supported service pack level, Extended Support includes […] Security updates at no additional cost”

Yeah, I search the AUR not to discover packages, but to see if something I want to install is in there, if it is I check the PKGBUILD and make sure none of the sources/commands/patches are suspicious.
People need to remember it’s not some carefully vetted app store and that they need to be the ones vetting any packages they install and any changes when updating.

They’re referring to the Enterprise LTSC IoT version: https://learn.microsoft.com/en-us/lifecycle/products/windows-10-iot-enterprise-ltsc-2021