Notable exceptions IME: the Pinecil, Pinepower, and Rockpro64. I haven’t tried their other SBCs though, and the Rockpro64 may be outdated at this point.

Drew mentions this and points out that it’s a new OS design and will therefore take a long time. He argues that an OS based on the linux design would be much easier.

Looks pretty good, but are you sure it’s open source? I don’t see the source linked anywhere on their website, and the “Description of Other Rights and Limitations” section of their terms of service suggests that it’s proprietary.