Hi @JSStoezel,
Thank you for contacting NXP Support.
Have you tried our latest SDK 2.14?
Here you will find examples for Cortex M7 using the RPMsg Lite library in the path middleware/multicore/rpmsg_lite
I will attach the link to this SDK. It is important to say that you will need to select your current board in this case for the Cortex M7 it could be the iMX8M Nano or the iMX8M Plus.
Welcome | MCUXpresso SDK Builder (nxp.com)
I hope this information will be helpful.
Have a great day!