If your recent attempt to update your Devuan system looked something like this:

Get:1 http://pkgmaster.devuan.org/merged chimaera-security InRelease [26.5 kB] Err:1 http://pkgmaster.devuan.org/merged chimaera-security InRelease The following signatures were invalid: EXPKEYSIG BB23C00C61FC752C Devuan Repository (Amprolla3 on Nemesis) <repository@devuan.org> Get:2 http://deb.devuan.org/merged chimaera InRelease [33.9 kB] Get:3 http://deb.devuan.org/merged chimaera-updates InRelease [26.5 kB] Err:2 http://deb.devuan.org/merged chimaera InRelease The following signatures were invalid: EXPKEYSIG BB23C00C61FC752C Devuan Repository (Amprolla3 on Nemesis) <repository@devuan.org> Get:4 http://deb.devuan.org/merged chimaera-backports InRelease [26.6 kB] Err:3 http://deb.devuan.org/merged chimaera-updates InRelease The following signatures were invalid: EXPKEYSIG BB23C00C61FC752C Devuan Repository (Amprolla3 on Nemesis) <repository@devuan.org> Err:4 http://deb.devuan.org/merged chimaera-backports InRelease The following signatures were invalid: EXPKEYSIG BB23C00C61FC752C Devuan Repository (Amprolla3 on Nemesis) <repository@devuan.org>

Then here's a fix:

1. apt purge devuan-keyring
2. rm -v /var/lib/apt/lists/deb.devuan.org*
3. wget http://deb.devuan.org/devuan/pool/main/d/devuan-keyring/devuan-keyring_2022.09.04_all.deb
4. dpkg -i devuan-keyring_2022.09.04_all.deb

Ta-da…

checksum:

sha512sum devuan-keyring_2022.09.04_all.deb 71254c56a97dfc457247bf25d671e716aa325c65b6ce7affa0f16e7498beca92ef9789d71cf3fd720402aaa27e830d16370d2101752308f37a594aa16f3def94 devuan-keyring_2022.09.04_all.deb