Can't update the system

[Elegant_Emperor]

I thought the no_pubkey error for edge was fixed in a recent release.
Well...I was wrong, perhaps.
This tutorial by @FrenchPress can solve that problem.

[HOW TO] Fix NO_PUBKEY error

Sometimes a manually added PPA could cause update error which looks like below during the update: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY XXXXXXXXXX This can be fixed by issuing the following 2 commands in terminal: gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv XXXXXXXXXX gpg --export --armor XXXXXXXXXX | sudo apt-key add -