- iOS 18 beta 2
- T-Mobile US, Verizon, or AT&T
- Most MVNOs are not compatible. If you do not already see the RCS switch in Settings > Apps > Messages, this will not work for you.
- Install
mitmproxy
- Download
redirect.py
mitmweb -s redirect.py --listen-port 8888 --ssl-insecure --allow-hosts jibecloud.net
- Configure the proxy on your device to use the IP address of the machine running mitmproxy and port 8888
- Go to http://mitm.it on your device, download the certificate, go to Settings, and then install it.
- Go to General > About > Certificate Trust Settings and enable full trust for the mitmproxy certificate.
- Turn RCS off (if applicable) and then back on. Wait a few seconds, then check for RCS in Messages. (Additionally, if all went well, you should see "RCS flow complete!" in the mitmproxy console.)
- Remove the proxy settings from your device and optionally uninstall the certificate.
Here is an example of a successful activation.

There seems to be no need to change the phone model. I have an iPhone 12 Pro, and it works just fine... That is after I did the Step 6 of enabling full trust for the mitmproxy certificate. So if anyone only sees the response with 511, it means they must have skipped step 6 like I did.
EDIT: This seems to be obsolete now, as RCS seems to be enabled on the Server side now for iPhones.