Marcin is a firmware developer on the Golioth SDK, which is based on the Zephyr SDK. He has worked in the embedded space for 10 years, 4 of those on Zephyr. Past upstream contributions have focused on the networking stack. He has an extensive background combining hardware, firmware, and the cloud.
The Golioth OTA service can handle more than just Over-the-Air firmware upgrade. This example application demonstrates multiple-artifact releases, where a picture to be shown on the screen of an IoT device is updated using OTA.
When it comes to automated testing, Zephyr's Native Simulator is worth your consideration. The next release of Zephyr will include offloaded sockets for Native Simulator, which means CI tests that complete many times faster than their native-hardware equivalents.
Golioth shows how to use Zephyr overlays and lays out a case for how they improve porting between different platforms, alleviating chip shortage issues.