You’re probably going to find that the terminal will come up at some point no matter what version of Linux you choose.
For most I would recommend Mint, but since you mentioned having a negative experience previously, perhaps Zorin OS would be a better alternative?
If you want a hardened OS that would be difficult to break, an immutable OS may be a better route for you. Here’s a link with some options to choose from. My recommendation would be Fedora Silverblue.
As someone else mentioned, you will still need to use a password when making changes to the system. You can set it to boot without a password if you prefer to. I use Bazzite (gaming focused immutable OS; based on Fedora Silverblue) and I want to say 90% of the time I only need my password at boot.
If you need office apps, LibreOffice and Open Office should do what you need. MS office can be a challenge to get running, but the online web versions will run out of the box.
Hope that helps!
I have a fairphone 4 and it hasn’t had any issues with the network since I first got it. Generally, any T-Mobile compatible device should work fine.
I would recommend checking their BYOD compatibility page for a more solid answer though.
If you want to verify a device you already own you can also type in the IMEI number and it will let you know immediately if it will have issues.