Just thought would record the challenges I've worked through so far, just in case anyone else gets stuck and might give some hints.
Software update not working via LuCI with from factory image.
Upon reflection I presume it some OPKG v APK fun; don't know where to start with that currently.
I then flashed the latest sysupgrade image via LuCI. Once it had completed, I lost access to LuCI; IP of the One was giving error connection refused.
Turns out the snapshot image (latest) does not come with LuCI, you need to manually install that.
SSH to the One's IP. I had already set a login, so used that. (Believe if you haven't password is blank.)
apk --update-cache add luci
Let that finish. Was now able to get back into LuCI via browser and software update via that is now working.
mkfs.ext4 /dev/nvme0n1
mkdir -p /mnt/nvme
mount /dev/nvmen01 /mnt/nvme
Then lost some time messing about and ended up remounting via LuCI's Mount Points.
Also struggled to see menu options for some of the installed packages. Reboot sorted that.
Created the samba share pointing at mounted path, allowed guest etc.
Was now getting warnings when trying to browse from Windows about insecure guest logons. Updated group policy: Computer Configuration\Administrative Templates\Network\Lanman Workstation\Enable insecure guest logons to enabled. Also think this regkey tweak would have also worked: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters\AllowInsecureGuestAuth = 1.
Could now browse the share with 'nobody' username but couldn't write / create files or folders.
Created sub dir and recreated samba share after running following.