iodéOS + root

Since v2.3, iodéOS uses user build type instead of userdebug(with the ability to enable additional debugging that normally violates the security model of the platform).
As a consequence root access and debug capabilities are no longer available in developer mode.

If you still want to have root access, you would need to flash a more permissive recovery such as TWRP & flash Magisk from the recovery using the following commands:

adb sideload Magisk.apk

And after reboot:

adb install Magisk.apk

I used the default sideload process and am rooted with the latest Magisk but no joy. Have hit the wall of understanding and unfortunately no joy here. Back to my iPhone 8+ for now until I can recoup enough patience and understanding again. Maybe in a year or two the problem may resolve itself. If only someone could add the Visible the global APN settings to the default APN list as I stated in the TeraCube forum under Visible + Teracube. But nonetheless, I digress. Oil well.

Another thought is that this does seem to be a Lineage OS related issue. Maybe in a year or two things will become clearer around this?