Version 8 of Veeam Backup for Microsoft 365 introduced proxy pools to improve performance and scalability in large installations. By logically combining several backup proxies, a proxy pool enables dynamic load distribution of backup and restore traffic, removing bottlenecks and accelerating processes.
Linux Backup proxy servers are auxiliary servers that you can configure to improve performance, scalability, and flexibility.
Veeam Backup for Microsoft 365 consists of Backup proxy servers, Backup Proxy Pools, Backup Local repositories, and Object storage repositories. These are configured as locations for Microsoft 365 backup data. These can be configured on-premises, in the cloud, or in a hybrid configuration.
Windows Backup proxy servers are auxiliary servers that you can configure to improve performance, scalability, and flexibility.
When you add an organization using the modern app-only authentication method, Veeam Backup for Microsoft 365 automatically grants permissions for Microsoft Entra applications.
Anyway, if you prefer to use a custom application of your own, grant all the permissions as below.