mobile

Hi everyone,
I'm trying to install a custom ROM on my AT&T Galaxy S4 and I have a few questions.
I've been using it on T-mobile so I haven't been able to get any of the OTA updates. (Which from the sounds of it, it sounds like a good thing.)

I'm currently running NC1. I also have safestrap installed on my phone. I'm assuming I can't install TWRP on AT&T Galaxy S 4?

Basically my question is,
Am I able to install any custom ROM at this point? Do I need to install specific kernels or anything further? I wasn't sure if I could install the 5.0.1 ROMs.

Sorry for the newb questions, I've been out of the rooting game for a while lol.

Thanks,
Indian