MMS feature is important for me. I'm willing to donate some money towards this bounty, maybe 20-50 USD.

@grhmhome

Sorry for bumping the thread (again), but I solved my issue. Since my old account was Sprint, it wasn't going to work out of the box, but I switched to T-Mobile and it now works properly.

@grhmhome
I figured out how to fix the issue I have. I bought this phone from a 3rd party (refurbish store) that unlocked it for US carriers. My issue is that my T-Mobile sim will not fully work. T-Mobile's website says my device is compatible, but it isn't sure if its unblocked. It will let me install a T-Mobile application for unlocking the device, but the application will not let me unlock it. I will probably bring it back to the refurbish store and swap the device or I will go to T-Mobile and have them unlock the device for me. After that, I can try installing Ubports, again.

@davedanger
I'm giving that a try, it might work. Before I reinstall UBports, I'm going to see if my simcard will even work in this android phone using build Android PD2A.190115.029.

@keneda
Thanks for the reply.
I made sure I was on 2g/3g/4g, but manually selecting a carrier will just say access denied after a while. I'm in the US, using a unlocked phone.

Hello there. I was able to downgrade my Pixel 3a to Android 9 with the Google rom flasher and install UBports, but I'm having an issue with it recognizing my sim card. I am on Sprint, but recently was given a T-Mobile upgrade sim card since Sprint is merging with T-Mobile. After I was able to activate that sim card on my Android phone (Samsung A71 5G), I decided to put the already activated sim card in my Pixel 3a running UbPorts. The issue is that when I go to carrier settings and select either T-Mobile or Sprint, it says denied. Is my new sim card compatible or does it not work? When I use it on my A71 5G phone it shows T-Mobile on top, but on my Pixel 3A, it does not. Is there a way to get this sim card to work or something I can reset in the terminal?

Thanks for your time.