Where can I find information for a USCC Galaxy S6 (SM-G90R04)?

There is no dedicated forum for this particular device here on XDA. I have just been referring to the general Galaxy S6 section for various things. I am having a difficult time really finding anything on the web. I have found a few things, but no real area of big support or community. I love US Cellular. They are a great provider for my rural area with great phone selection (got this s6 with an otter box COMPLETELY FREE with their points system... no contract extension needed), but with that said, I understand that they are a small regional provider. So far I have been able to flash ROMs on my phone with the hopes of having them work, and they do actually... except I can't get any mobile data, voice, or SMS.