Phew! I just had some very exciting moments doing the upgrade. I decided to take the conventional method using TWRP. This is how I did it:
- deactivated screen lock (but forgot to deactivate SIM pin...)
- installed TWRP using fastboot
- booted into TWRP and made a full backup onto a USB memory
- made sure that backup could be restored
- wiped system partition and cache
- installed the image and MtG, that I had copied on the same USB before
- wiped cache again
- rebooted system
System started, but when SIM pin was requested, system rebooted instantly. Bummer!
- rebooted into TWRP
- deleted the lock db
- removed SIM
- rebooted system
System came up and was running and all apps where still installed. Great! After a few moments I inserted the SIM and was asked for the pin. The SIM was unlocked and network was working! Hurray!
After playing with the phone for about half an hour now there's only one think I'm missing: there used to be an option to kill an app by holding down the back button for some seconds. I can't find that option any more. Has it been removed?
On the other hand, there are two apps now, that I would rather not have on my phone: Google and voice search. I assume they are part of the MtG package. I can not uninstall them. Will I be able to get rid of them by reinstalling the LOS image plus OpenGaps Pico, once those package is available? Or will installing OpenGaps break any dependencies?
One error message keeps reappearing saying "DM config update failed". Should I be worried about this? What to do about this message?