W10 LTSB is not EOL’ed, far from that. 10 years in future TBH.
8.1 is not EOL, yet (not mainstream, but still).
And even MS tells that ONLY difference between 1.3 and 1.4 DirectML is redistributable package, so… Yeah, better build with old library version and refuse to upgrade, just because, you know, software development pipeline does not build software daily, just because this cost money 