Follow Below guide on how to install unofficial Cyanogenmod 13 (Cm13) rom in HTC One M7.Before flashing Do check the Bugs and stability report of this rom from XDA Thread here.As of now rom is not for daily use and having lots of bugs in it.Check below bug list in CM13 for HTC One M7.
1.Camera doesn’t work
2.Calls don’t work
3.Microphone doesn’t work
4.Bluetooth doesn’t work
#How To Flash Cyanogenmod 13 rom in HTC One M7
2.Now place the Cyanogenmod 13 rom and gapps 6.0 zip file in sd card.
3.Now reboot to Recovery mode and flash Android marshmallow rom in your device.
4.Then flash CM13 android marshmallow rom and gapps from recovery in it.
5.Now Clear cache and Clear Data.(Full Wipe Preferred)
6.Reboot your device.Done! you just flash cyanogenmod 13 rom in your HTC One M7 .Enjoy Android Marshmallow 6.0.