1) How do I find out what I'm running ?

I guess the answer to this is rpm-ostree status, but what does
it actually tell me ?

● atomicws:atomicws/fedora/x86_64/continuous
                   Version: 26.447 (2018-01-29 04:58:49)
                BaseCommit: ba986d4649f08705185ba1ce7208e72d149b1e35314d112a86348cb1d61f6f52
           LayeredPackages: powerline

It would be nice to explain this output a bit - I assume the first 'atomicws' is a repository name, and 'atomicws/fedora/x86_64/continuous' is a branch name. Version 26.447 may indicate that I am running some version of Fedora 26.

Unfortunately, I haven't really seen the gnome-software support

in action yet, but I hope it shows this information as well.

2) How do I get the latest updates ?

rpm-ostree upgrade is easy enough (once I've found it).

3) How do I upgrade to a newer release ?

4) How do I find out what branches are available to rebase to ?

5) Where is the repo configuration stored ?

This is where I got stuck - I could not find any answers to these.

Very frustrating, a normal user would have given up here.

Eventually, Kalev told me to create a file in /etc/ostree/remotes.d/ with some content, and then I figured out to run

ostree remote refs fedora

to see the branches in the repo, and

rpm-ostree rebase fedora:fedora/27/x86_64/workstation

to upgrade to one of them. I blindly picked this branch, since

I have no idea what the difference between

fedora/27/x86_64/testing/workstation

fedora/27/x86_64/updates/workstation

fedora/27/x86_64/workstation

might be...

Also, I had to disable gpg verification, since I didn't know where

to find the key for that repo.

We need to make the rpm-ostree plugin support distro-upgrades

inside gnome-software. And also make this information available

in some obvious place.