For Kopia, back up a representative set of files, including a large file, a frequently changing directory, and something with important permissions. Restore to a clean location and compare checksums and metadata. Repeat after a simulated accidental deletion and after rotating or recovering credentials.
Record repository location, encryption key custody, retention settings, and the expected restore time. Backups are only useful if an operator can recover the right version under pressure; a green scheduled-job status is not proof.
Akousa