Hey, gkrc717! I haven't heard of anything like this before -- and I definitely agree, a fantastic device like this should work on LTE. Are you still having trouble with this? I know it's been a few days since your post, did you wind up moving forward with a Master Reset? I understand saving that as a last resort -- what troubleshooting did you try already? APNs typically aren't an issue with a T-Mobile branded device, but resetting them can't hurt! Did you do a cache wipe as well? What about testing in Safe Mode? Please let us know if you're still having trouble!
I just wanted to swing by one last time to see if this is resolved. If you're still experiencing the issues with your S8 and MMS, please take a look at the questions Marissa posted above and get back to us. Thanks!