How would I be able to do the same but without another carriers SIM card? I only have my T-Mobile SIM card which is activated.
@RedDragon Thank You for your advice! I FINALLY got it to update! I found my old AT&T sim card, and used that. I had to pop out the T-Mobile sim card for the AT&T one, reboot twice, then did all the updates that were available. Then I swapped sim cards again and rebooted twice to be able to use my phone again on T-Mobile. (The AT&T sim card was deactivated, but that did not seem to be an issue with getting the phone to get the updates it so desperately needed.
I already have other reasons to go reach out to T-Mobile and express my concerns and tell them what-for, because they apparently decided to deactivate a tower and I no longer get service at home without using WiFi calling which they told me wouldn't work, HA guess they were wrong, buthaving no service in my neighborhood is a pain, and with this update blocking, I will probably go back to AT&T or maybe even give Verizon a try.
It did not seem to be an issue that the old sim card was deactivated so hope this helps other people, and they can get updates and more importantly security patches on their unlocked phones on T-Mobile.
@Berserkr78 Try to remove the sim card and update through the wifi, if not then you need to borrow sim card even if it's non active it will work.