Hi Myke:
MCUXpresso SDK can support MK22 with FreeRTOS. You can download SDK from below link
https://mcuxpresso.nxp.com/en/select
For MQX, now current version is MQX v5, it is under commercial license. Please check below link for more details
MQX™ v5 Software Solutions | NXP
MQX v4.2 is the last release in MQX classic product line. MK22 is supported. You can create a case to contact NXP.
https://nxpcommunity.force.com/community/
Regards
Daniel