Not that I would recommend it but you can purchase LTSC on Ebay for about ~20 to 30$. That is where I got mine... Sketchy? Yes, but worth a chance in my book
Doesn't sound like you purchased it. It sounds like you gave some [random] place money for a pirated (and maybe backdoored) copy of Windows.
That's likely a very bad approach. ;)
Updates work just fine and are only performed at reasonable intervals
But, please don't encourage others to put themselves at risk. aka fall for a scam on Ebay
you could get scammed or have your key deactivated a hundred times and still be ahead
At least, not without (at a minimum) having the SHA256 (or better) checksum of the ISO match that of the MSDN equivalent download.
and there's plenty of dumps of them kicking around if you don't