Is using voicemeeter cheating in Apex Legends?

Actually the way "Easy Anti Cheat" works is a lot like a virus scanner.  It checks your system for "known cheats" and looks for patterns.  Then it reports suspicious activity to a human via a log. Although it might have the ability to automate bans to reduce the cost of human labor.  I am unaware of what options the developer has with EAC.  I suspect the publisher (EA) is the one in charge of the bans and would be the ones in charge of how it is set up.

The strange thing about 3rd party software is the loose definition of it.  Legally speaking any mouse or keyboard driver installed other than by MS Windows is considered to be 3rd party.  To run Apex and many other games, I have to use Steam Proton which allows Linux OS to run Windows games.  It is almost impossible to run any game without some 3rd party tools in the mix.