Just another useless list.
It will be interesting, how long LG will update our G2. I know there is marketing, but they must know LG G2 is their probably the most successful phone. But if we get Android M, I'll be really surprised! :D
It you font have this function in your SIM settings, just dial *#800#, then tap "oneplus Logkit", "Function Switch" and then tick VoLTE and VoWIFI Switch, reboot and voila... :)
Here is the link you wanted to give with that unofficial english firmware: https://www.reddit.com/r/miband/comments/8r88c7/unofficial_english_firmware_for_mi_band_3/
No one knows, unfortunately. Except LG itself.