Okay dokay, I got bunch of help from posde in #linuxmce.
My installation turned out to be a very old one, therefore massively outdated and not really suitable for normal update. It required some sort of package etc magic, I was just repeating the commands instructed. After a few reboots, the system is up and running again.
Thank you for your help, I hope to contribute back soon.
BR, Kooma