BeagleBoard is similar to RaspberryPi, but focused on embedded robotics vs desktop PC alternative. The PocketBeagle is similar to a Pi Zero. Fully open source hardware. Smaller community though, so harder to find examples/capes. http://beagleboard.org/boards

Artemis seems to be Sparkfun’s new line of Feather-compatible boards. They target a pro-level audience vs Feather’s edu audience. The OpenLog Artemis looks interesting for logging telemetry. https://www.sparkfun.com/news/tags/artemis