[Khesarr]

New firestick does not need a shitty build. It does DTS / AC3 by default.   

My Firestick 2017 incl. Alexa didn't do it with official Kodi 17.3, that's why I'm on shitty. I don't know anything about the new 3rd Gen Fire TV, though.

Or does this mean the 18.x nightly versions again include DTS passthrough? With 17.3, DTS wasn't even in the settings on my Kodi/Firestick set.  

No. We support proper SW implementation.  The new firestick (released 8 weeks ago) has proper DTS support. The older FireTV sticks don't. As amazon does not want you to have them. BTW. they patched OUT DTS in RAW mode again from the 3rd gen, but did overlook the new IEC format ... that's the only reason that stick will have DTS supported. If you did not get that yet: amazon only wants to provide to you the limit implementation to fully play THEIR content and nothing else.

I don't even understand why one would support such a company, that does everything to break the SW (Android has good working DTS support since more than 1 year now) ... 

I didn't try with the new FTV stick yet (connected to a stereo only device) but the newly released Fire TV with 4k support has some major audio issues with Kodi 17.6 (same for 17.5, didn't try older releases on it). Whenever I activate pass-through I have no audio at all most of the time, regardless the input, showing PCM2.0 on the receiver. I have to disable pass-through and then the sound gets converted (!) to DD 3/2, again regardless what's the input. Sometimes AC3 tracks get through fine.
And no, I didn't activate transcoding. Simply set speaker configuration to 5.1.
It's working quite OK most of the time but video stutters/freezes on higher bit-rates (?, scenes with smoke or much action), although the network is working fine on 5GHz (2.4GHz is a mess with constant freezes). I have a 100 Mbit throughput on WiFi from the Internet on 5GHz, around 34 on 2.4GHz so I'd expect to have even more from my NAS but still these freezes. Higher chance of freezing when playing DTS.

I bought the new Fire TV because I was expecting that the audio issues will be gone as the device is running on Android 7.1 with API level 25 but sadly, it's still the same as on the older models with API 21.