Where can I find the source code of the running official devel image and the currently not working official rc-proposed image (which seems to behave the same like the Ubports image) ? The old devel image is really outdated and I would like to get running the current rc-proposed image. In a first step I would try to find out where are the changes and what leads to the boot loop. It is really annoying that BQ comes out with an ubuntu M10 tablet while the Nexus 10 has a better screen but the working ubuntu version is outdated and the current version isn't working Is there someone in the community who would support me with knowledge to debug the current rc-proposed images ?

Same problem here. Only the official "devel" images are working. With the Ubports images I'm running into the same problems like user gspublic. I tried with and without --bootstrap. The official "rc-proposed" images are ended up in a boot loop showing only the "google" screen.