I am using Syncthing happily on Kubuntu and Windows. All worked well for 2 years until last week I started to get on the kubuntu machine:
E: Conflicting values set for option Signed-By regarding source https://apt.syncthing.net/ syncthing: /etc/apt/keyrings/syncthing-archive-keyring.gpg !=
E: The list of sources could not be read.
Any idea where to start to fix this? I have been reading the documentation and searched for a solution and I still have no idea how to fix these as all look normal.
You seem to have several files pointing at the same APT source, but not identical. I’d try grepping for (part of) the URL in /etc and removing / editing all matching files. Then start fresh by following the instructions at the Syncthing APT website.