After installing an update to Veeam Backup & Replication, the Linux (Mine-based) repositories within the Backup Infrastructure become marked as "Out of Date," and attempts to perform Component Update fail with the error:
Permission denied (publickey)
This is expected behavior. Veeam cannot upgrade the Veeam Data Mover Service directly because (per Mine 3.0 Release Notes) SSH access is disabled on Linux repositories by default. The Veeam Data Mover Service must be updated within the Mine console (see Solution below).
The Veeam Data Mover Service for Mine-based Linux repositories can only be updated through the Mine console.