I think it come with the 1.4 release: https://csa-iot.org/newsroom/matter-1-4-enables-more-capable-smart-homes/

Enhancements to Battery Powered Devices:
Matter 1.4 introduces core enhancements that optimize battery life and communication for Intermittently Connected Devices (ICDs) like switches, buttons, and sensors. Key updates include the Long Idle Time (LIT) protocol, which extends battery life, and a new Check-In Protocol to ensure reliable communication for low-power devices that require LIT. Additionally, quieter reporting of predictable attribute changes reduces network traffic, resulting in improved battery performance and network efficiency.

Developers interested in learning more about these enhancements can access the following resources:

Matter 1.4 specification and test plan
Matter 1.4 SDK Release

Hi - surfacing this post. Is there a plan/timeline for Intermittedly Connected Devices (formerly Sleepy Devices) to be supported in the Arduino codebase?