Here is what worked for me:
(I am on a Pixel from the Google store using a Verizon sim on build NDE63X / bootloader unlocked / rooted / on EX kernel)
While the phone is turned on (NOT in download mode), open minimal ADB and push these commands:
1.) adb shell
2.) su
3.) mount -o rw,remount /system_root
4.) cd /system_root/system/
5.) settings put global tether_dun_required 0
6.) echo net.tethering.noprovisioning=true >> /system_root/system/build.prop
7.) adb reboot
Also note, adb reboot command did not reboot my phone, so I did it manually and it worked out fine.