Comment by pajko

RISC-V, ARM in development: https://en.wikipedia.org/wiki/Haiku_(operating_system)

https://en.wikipedia.org/wiki/AROS_Research_Operating_System

https://en.wikipedia.org/wiki/MorphOS

https://en.wikipedia.org/wiki/AmigaOS_4

https://en.wikipedia.org/wiki/Inferno_(operating_system)

https://en.wikipedia.org/wiki/Illumos