How can I backup to my iPhone to a network drive?

Is there a way to backup iPhone to a network drive?

Yes.

If you use iTunes on a Windows-PC create a JUNCTION LINK "mklink /j". This example will backup to OneDrive.

cd C:\Users\peter\Apple\MobileSync\
rename Backup Backup-OLD
mklink /j Backup C:\Users\peter\OneDrive\Apple\MobileSync\Backup
move Backup-OLD\* Backup\

You of course have to create the folder on OneDrive

mkdir C:\Users\peter\OneDrive\Apple\MobileSync\Backup

You can also backup to a network drive. You have to map a drive letter because mklink does not support UNC paths.

net use   N: \\pS-NAS\homes\Peter
cd C:\Users\peter\Apple\MobileSync\
rename Backup Backup-OLD
mklink /j C:\Users\peter\Apple\MobileSync\Backup  N:\Apple\MobileSync\Backup
move Backup-OLD\* Backup\
mkdir N:\Apple\MobileSync\Backup