Sim cards and carriers, discussion

[bcnaz]

Just for curiosity,  perhaps  try running from a fresh sd card ?

On my Manjaro phone, I had no problem finding and adding the APN information,
( I am running a recent release of Manjaro/Phosh on an sd card in this particular phone)

Though I am running Manjaro/Phosh from an sd card,  I would imagine it should operate close to the same with the KDE/Plasma.?
(Maybe if yours a factory install, it may need to be updated ?)

For personal reasons I do not like Tmobile,
  However, in all fairness,  I have found them to work fairly well and easily when I tested them in my Pine phones.

But I have not tried any Plasma desktops.

GOOD LUCK