SQL Server 2016 - write output file to mapped Samba share (CentOS 7)
In order to map a network drive under the SQL Server Service Account, you need to login to the server as the service account.  Then use net use /persistent:yes to connect the share.  This should make the share available to the SQL Server Service Account automatically each time it logs into that server.

Having said all that, instead of using a drive letter for the share, simply write directly to the Linux SMB share via the UNC name... so \\linux-machine\share\some-file-name.csv

Alternately, as Aaron Bertrand alluded to in a comment, write a utility to query the data from SQL Server and write directly to the samba share on Linux.