Some of the most important micro-ROS features that are available with micro-ROS Iron release are:

• Micro XRCE-DDS v2.4.0
• new support for RT-Thread
• upgrade Espressif ESP-IDF support to ESP-IDF v5.0
• upgrade Zephyr support to Zephyr v2.7.0 and v3.1.0
• upgrade micro-ROS for Arduino library
• Deprecation of micro-ROS Galactic and Foxy
• huge amount of bug fixing that makes micro-ROS a ready-to-use solution for embedded ROS 2

Release track here