Yes, they do appear to be miscategorised, thanks for spotting that! @roadmr or @toto can probably help there (these are actually Operator Framework Kubernetes charms)
As for example machine charms using Operator Framework:
This week I’ll continue work on porting the
hello-juju charm. I’ve started work in this branch. I still need to write a decent README and implement the relation and some tests. The relation should be done today! This will get published to Charmhub when complete.
You could check out the Ubuntu Advantage charm (it’s a subordinate charm). See source code / charm store .
Another is the MicroK8s charm source code / charm store.
Looks like those last two haven’t been pulled across into Charmhub yet. I guess @mthaddon may also know of some more Operator Framework machine charms.
Those three tutorials sound great! Have you seen the latest developer docs? They don’t cover everything you mentioned, but there is definitely a start on the basic constructs of Juju. You can also contribute directly to those docs through Discourse if there is anything specific missing
(Forgot to include a link that documents how to contribute great tutorials )