I stumbled on this on /r/programming this morning:
https://zyedidia.github.io/blog/posts/1-d-baremetal/
There's a follow up post focused on VisionFive 2 here:
https://zyedidia.github.io/blog/posts/2-baremetal-visionfive/
And the author is developing an OS in D called Multiplix:
https://github.com/zyedidia/multiplix
Cool stuff!