I am seeing errors like that below from apt since yesterday
evening.

Err:4 http://deb.devuan.org/merged beowulf InRelease
    The following signatures were invalid: EXPKEYSIG BB23C00C61FC752C
    Devuan Repository (Amprolla3 on Nemesis) <repository@???>

Have the repository signing keys changed?

Suggestions gratefully received for fixing this.

Best wishes,

     John