[Nexus 6 Android Development] relaxable:
I see same thing - Verizon APN has most of the fields greyed so can't edit any existing entry, and there is no option to create a new APN.

I put a different SIM in the phone (without powering off), and after the SIM is recognized, the APNs for that SIM are complete & editable, and I'm allowed to create a new APN. So, I created a new APN, "test", and saved it. Then, I switch the SIM back to Verzion, and my newly created APN disappears, back to not being able to do anything with Verzion/APNs. (The only option is 'Reset' which brought in a longer list of useless and un-editable APNs.)

Is there somewhere (with root) that we could go to get the right info in for the APN? Or does it have to be done before the ROM is built?

I notice there seems to be similar(?) issue with Nitrogen OS and Verzion.... (Actually, I flashed Nitrogen, and it's even 'worse' there - no APNs show at all for Verzion and can't create any, and can't get any Internet access except by wifi)

Edit: Interesting - with Verizon SIM in Nexus6 running Pure Nexus ROM 7.12, the Verizon APN is not editable, and cannot create a new APN either. The MMS settings in the APN have no values either, BUT, I can send MMS.... So, I think this isn't really the APN issue??

Also: https://www.reddit.com/r/GooglePixel/comments/6xiijs/oreo_verizon_mms_broken/ implies that APN settings aren't used/needed for MMS?

And, see this: https://productforums.google.com/forum/#!topic/phone-by-google/fiR08FaHm_8

Edit #2: From https://support.google.com/pixelphone/forum/AAAAb4-OgUs_PGJbTEuY0M/?hl=by (post from 11-5)

Kleinsmith LP
Inability to edit APNs is the future of android, unfortunately, in that this inability first appears in the transition from Android 8.0 to android 8.1 (i.e., Android 8.0 on 1st gen Pixel XL doesn't have this issue, but Android 8.1 on 1st gen Pixel XL does have this issue - Yes, we recognize that the Pixel 2 XL is running Android 8.0, which is why we call it a transition issue).

The apns-conf.xml file (found in /system/system/etc or /system/etc) is what populates all the APNs under the Settings app. There is a new setting in the apns-conf.xml file (found in /system/system/etc or /system/etc), which setting is labeled "user_hidden" with options "true" and "false". All of the Verizon MVNO settings are labelled as "true", meaning that APN editing access appears to now be restricted.

There is no way that I know of to edit this apns-conf.xml file without bootloader unlock and root.

And, it's definitely an Android issue, as Android 8.0 and earlier did not have this issue.

Speculation on my part, but this is probably Google's response to its exclusive carrier, Verizon, request that these phones not be made easy to use on much-cheaper-than-Verizon MVNOs.

P.S. Thank you Katerina for the practical work-around; as an FYI, the name on the APN setting can be anything desired.

Then, I found this post which provides a way to actually change the non-changeable APN settings - see post # 8 at https://xdaforums.com/pixel-xl/help/android-8-1-how-to-edit-cellular-apn-t3697425 and I put the "right stuff" in for Verizon MMS, and still can't send MMS!!!!

ALSO - Wish there was a toggle to turn off that huge/ugly VoLTE icon in the status bar. NitrogenOS has toggle for it, but the toggles for these icons in this rom are in System UI tuner, and there is no option to get rid of the VoLTE icon which takes up excessive amount of width in my opinion...! (I guess this is a Lineage OS thing?)