ok, i have similar problem with asus Zen Max Pro (M1) - there are default settings for telus and kodo and no way to change them. Also impossible to add new APN, as error pop up: "operator does not allow adding apns of type *".
Looks like glitch with Android 8.1. At least this forum helped: https://www.reddit.com/r/mintsim/comments/78usic/my_pixel_2_is_saying_the_carrier_doesnt_allow/
In short fix (workaround/hack ) was like this:
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Just bought a Pixel 2 and wanted to edit APN settings but the edit settings are greyed out and I can't change anything. The settings don't match what PM has listed so wanted to tweak them. I also don't get the add APN settings option (the plus sign).
-------- And here is answer : ---------------------If you're still having issues with this, I found a solution that works on my Pixel 2 running Oreo. When you go to create the APN, put all the info from Mint's site in. Instead of tapping Save, back out with the Home (circle) button. When you check your APN list again, it will be saved with the correct settings (if you tap on the APN name to view it, use Home to back out again, otherwise it'll come back up with the error). Select the APN to enable, should work fine.
