I’m a longtime user and and fan of syncthing. I recently followed the instructions at https://apt.syncthing.net to add the syncthing ubuntu repository and install syncthing on a new computer. At the time, it succeeded. Now when updating repositories, I get this:
# apt-get update Get:1 http://security.ubuntu.com/ubuntu bionic-security InRelease [88,7 kB] ... Err:9 https://apt.syncthing.net syncthing Release Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate. Could not handshake: Error in the certificate verification. [IP: 18.104.22.168 443] Get:10 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74,6 kB] Reading package lists... Done E: The repository 'https://apt.syncthing.net syncthing Release' no longer has a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.
The issue remains even if I re-download the release-key.gpg, or if I remove the [signed-by=/usr/share/keyrings/syncthing-archive-keyring.gpg] part of the apt source line. I am using the stable channel.
I also notice that on another computer, the same apt line (without the signed-by part) seems to work (?!) so I’m not sure what gives.