[tremon]

with open source libraries/ reference implementations

Citation needed? FAFAIK the reference implementation is closed source, and there are no libraries -- only a powershell module that is actually a wrapper around the Word/Excel OLE objects.

[nxc18]

https://github.com/OfficeDev/Open-XML-SDK

[19870213]

There is Apache POI for the JVM.

https://poi.apache.org/overview.html

[selckin]

Uh no, barely works for even the most basic tasks