I use this minimal one. Check out what Waveshare has to offer too.

https://sourcekit.cc/#/

Thanks… my ideal would be a similar sized carrier with PoE and M2 support

Think I really want something like the Uptime Labs Blade https://pipci.jeffgeerling.com/boards_cm

What's a carrier in that context ?

An IO board that adds the IO ports that the e.g. CM4 lacks. There's a decent range of them from different suppliers, but Raspberry Pi have one themselves called "Raspberry Pi Compute Module 4 IO Board".

Thanks !