hasn’t even been any commits in 4 months — is k3os still active / part of the future with rancher ?

It's dead. The maintainer is not working at Rancher anymore and apparently Rancher has no intention of making this a product

What are the options you know of to run k3s tightly coupled w/ an OS ? do you know a reason it died?

I mean I just told you, the maintainer left Rancher...Rancher has also been bought by SUSE which has their own OS, so I can see why they would not want to invest in another OS.

Thanks @prehistoric-barista-70029

Take a look at https://github.com/rancher/elemental it's ROSv2 or to https://github.com/c3os-io/c3os

Another option is MicroOS, which SuSE have promoted as the replacement to K3OS. I'm working on integrating my stuff with MicroOS right now

what’s your experience with MicroOS so far?

My apologies for the very late reply. I’ve integrated my stuff with MicroOS now. • The snapshot filesystem (btrfs) seems great • Upgrades are a little harder because K3OS writing from a docker image was much easier. I had to create an RPM mirror and rsync the opensuse mirrors, but it works • using Ignition/Combustion is much better than cloud-init. It runs once but is much more powerful (but if you boot without the Ignition volume, it wont run Ignition again until you delete the first_boot_happened marker file) • Installing k3s on it was a little awkward (you add the Rancher RPM repo, install k3s-install, then run it) but I got it working • You can install tools on the OS, which is much more convenient than K3OS • Auto-upgrades and reboots using KuReD is working great