How to get a Spektrum transmitter to work on a Apple Mac OS X (also the newer Macs without audio optin) with simulators like Liftoff, Free rider, DRL, Velocidrone etc etc.

Very easy ;)

I personally tested a Spektrum DX9 and a DX6i with both Liftoff and Freerider on a 2016 iMac 5k as well as on a 2016 MacBookPro. All worked perfectly fine. I am sure it would work with all Spektrums. ;)

Update February 2017:
If you wanna go wireless and spend a bit more money, Spektrum just just released word of a new product that will be launched in May. There own dongle!
http://www.horizonhobby.com/wireless...