You can also get the iso direct from Massgrave's site, along with the KMS activator. Your choice, but I do expect the people behind the Internet Archive to have checked for malware in some capacity. They do have a legitimate research and archivist reputation to uphold.
I'm pretty sure the final version of Windows 10 LTSC 2021 had its window of support shortened to five years to align with the end of support. Only windows 10 LTSC 2019 has 10 years of support. If you're using LTSC 2019 for gaming please be aware you will be missing any features released for windows 10 that were released after version 1809. This will harm game performance for a lot of newer titles and hardware.
I’m on IoT Enterprise LTSC 2021. As far as I’m aware it’s up to date, and if not I don’t really use my PC for modern games anyway. Still good to know though.