Give UNC folder permission for Virtual Account

to allow restore DB from the backup file from another SQL server machine

Configure Windows Service Accounts and Permissions

https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/configure-windows-service-accounts-and-permissions?view=sql-server-ver15#New_Accounts

Virtual Accounts

Virtual accounts (beginning with Windows Server 2008 R2 and Windows 7) are managed local accounts that provide the following features to simplify service administration. The virtual account is auto-managed, and the virtual account can access the network in a domain environment. If the default value is used for the service accounts during SQL Server setup, a virtual account using the instance name as the service name is used, in the format NT SERVICE\<SERVICENAME>. Services that run as virtual accounts access network resources by using the credentials of the computer account in the format <domain_name>\<computer_name>$.