I managed to open the SIM slot of the phone and inserted a working SIM from another phone. Since the SIM was not detected at all, I decided to give the nightly CynogenMod 12.1 on the phone. Again via SFTP to SSHDroid in the LAN.
An Optimus G E975 (Intl) was still waiting for wakeup, but official updates stuck at Android 4.4.2.
So I applied CyanogenMod to that phone and since it was not that easy to gather all the necessary information, I write down a short protocol of the steps, that helped in my case. I started with the rather incomplete (with respect to rooting and recovery) howto at wiki.cynogenmod.org.
It was time for another update from https://github.com/nadlabak/android/downloads.
It was just about time to update my Motorola Milestone to the latest CyanogenMod, providing Android 2.3.7.
Please find the final CM7 release at the usual location: https://github.com/nadlabak/android/downloads
Waiting for the upgrade to a newer post-2.1 Android by Motorola, I heard rumours about the Android 2.2 released recently, that were not very positive with respect to quality.
So I decided to get Android 2.3 via CyanogenMod on the Milestone with the help of OpenRecovery G.O.T..