I haven’t proved volte until now (idk why), but it doesn’t work either. About the camera problem that I’ve reported on my previous comment, I’ve been reading some posts, and somebody create a flashable zip with a “solution patch” (which basically consists on replacing a system file related with camera sensor). Flashed it and guess what, it didn’t worked. Instead, camera app isn’t working at all (it crash with “stop responding”).
Now, switching back to Lineage 13.0 (Marshmallow) and waiting until 14.1 is a little bit more stable.