There's a range of DDS implementations, definitely a number that are compatible with embedded and spaceflight applications that don't require dynamic memory allocations. You're going to take a hit on some DDS features, but then again you aren't going to need to handle a large queue of large dynamically-sized messages on some small embedded platform.

I think it's rarely the right choice - most of the hardware I've seen that uses embedded DDS probably should have used plain old UDP instead and then whatever client was running on beefier hardware then handled the translation into DDS - but there are shipping products that use embedded DDS.

Zenoh (https://zenoh.io/) is a good alternative to DDS in many cases - it scales down to microcontrollers with most features still intact, but scales up to a routed hybrid mesh if needed.

It does move the schema enforcement out of the middleware layer, so it’s a bit different. But it’s now a first-class alternative middleware implementation for ROS2 as an alternative to DDS.

Pretty sure there are DDS implementations that provide most of that, maybe with memory pools instead of no-allocations.

Other than that, PX4 uses an in-memory only pub/sub for internal data bus, somewhat inspired by DDS