apt-get update
Get:1 http://deb.devuan.org/merged chimaera-security InRelease [26.5 kB]
Err:1 http://deb.devuan.org/merged chimaera-security InRelease
  The following signatures were invalid: EXPKEYSIG BB23C00C61FC752C Devuan Repository (Amprolla3 on Nemesis) <repository@devuan.org>
Reading package lists... Done
W: GPG error: http://deb.devuan.org/merged chimaera-security InRelease: The following signatures were invalid: EXPKEYSIG BB23C00C61FC752C Devuan Repository (Amprolla3 on Nemesis) <repository@devuan.org>
E: The repository 'http://deb.devuan.org/merged chimaera-security InRelease' is not signed.
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.