@stephenshutters which US Mobile plan do you use? I am on Dark Star and having issues receiving group messages. Checked my APN settings and there is info the MMSC/MMS proxy/MMS port/MCC/MNC fields so I am not sure this is the crux of my issue.
The main problem for me is that other peoples phones are sending RCS in group messages. Occasionally a stray MMS message will come through. No issues that I am aware of with individual messaging.
I also am on Dark Star. You can view my APN settings in this comment I made in a separate thread.
When it comes to RCS issues, here is another comment I’ve made regarding my discoveries in that regard.
thanks for the quick response. I copied your APN settings and that actually appears to have resolved a different issue I was having with my data services not working! thank you 
Regarding group message tip - do you mean that each person needs to delete every group message with you in it off their phone or just the specific group message in question? ie if I have a group message with 2 people and they both delete that thread off their phone it should resolve the issue in your experience?
In my experience, every single person involved in any pre-existing group threads with your number needs to delete all of those group threads. Then you personally need to start a new group thread to replace the ones they all deleted. I know it sounds absurd, but it’s the only thing that has worked for me to overcome RCS issues.
I got a mint mobile plan specifically for my Kompakt since US folks seemed to be having issues with pretty much every major carrier. I believe T Mobile would work as well since Mint uses the same network. The mint setup was super easy. I got a 45 dollar plan + SIM card at target, activated the SIM card on my computer using the web app (they have an android app but it requires google services so cant run on the kompakt), plugged it into the phone and updated the APN settings according to mints instructions and everything has worked flawlessly. I have been sending and receiving photos, group messages, etc without any issues.
It also seems like in the majority of forum posts where people are having issues, its when they are transferring a SIM from one phone to the kompakt. Even after disabling imessage, RCS, they still have problems. It sucks having to get a new number, but this way I was able to keep my iphone for travel/emergencies for when I need something with more capabilties.
Hi @urszula yes I have and I have also set up APN, but still not receiving group chats or images. Constantly receiving MMS delivery failure messages
How is your connectivity/coverage on Mint Mobile? I have Verizon and am often getting low bars, which I didn’t used to on my iphone. Do you have mostly high bars and do you recieve images in texts without problems?
Connectivity is good. Im in Austin and have about the same coverage as I do with ATT on my iphone. I get MMS messages, group chats, etc just fine