You can remodel your Chinese M8sw following this thread. If you run into problems then check out my post here.
1. Make a TWRP backup of your current system to your SD card. (This sets up the correct file system you need and also a good safety measure)
2. Unpack the TWRP I have provided and copy to your SD card INTO THE RELEVANT FOLDER!! (Next to your previous backup)
* PARANOID MODE *
Perform a factory reset and then reload your previous backup so you can check it’s working OK then go to 3.
* LAID-BACK MODE *
3. Do a FULL wipe but do NOT reboot.
4. Reload the TWRP with Marshmallow.
5. Reboot
6. Enjoy 
Please make sure you don’t factory reset otherwise you’ll lose root. That case go to recovery and flash superSU again.
Rom Information :
Android 6.0.1
HTC Sense 7.0
Software 3.07.401.1
Stock Kernel 3.4.0
Rooted
Permission & Terms :
Feel free to use it but please note that all the usual legal crap applies: YOU ARE responsible for your own actions I am only providing the means to screw up your device. Only do this if you know what you are doing. (BTW this is a good advice for another aspects of your life as well)
Credits :
@HTC to finally release it…
Download from here.
Deleted apps (you can either install them from Google Play or download them from above link and place them in their location):