Wondering if this is related to this bug where data connectivity drops even though it looks like the phone is still on the network?
I don’t think so, as I said, the phone itself did have working internet. E.g. I could browse the web on the phone just fine while the laptop could not. I did try your procedure, but it made no difference. Still no shared internet.
I also did not try VoLTE yet.
defaultuser isn’t root - try devel-su (with developer mode enabled) and enter your SSH password
While this does work, why on earth would ping require root access?? 