I want to back up some Windows machines to my QNAP NAS using Restic.
As far as I understood, SMB isn’t supported (unless I map the drive, which I don’t want to do due to the risk of Ransomware).
I have set up SFTP on my NAS instead - but where would I place the private key or password?
I would be using Backrest, Resticprofile or Restic Backup GX, but I guess that shouldn’t matter as they are all just wrappers around Restic.
Do I need Plink?
For restic and SFTP you should check docs - Preparing a new repository — restic 0.17.0 documentation
As for other software you mention I think you could ask on their forums.
In case of SMB you could use rclone - and then use rclone with restic Preparing a new repository — restic 0.17.0 documentation
I think you missed the part where I mentioned it’s about Windows clients. The documentation only explains the setup for Linux clients.
Search this forum. People posted full recipes in the past.
Hey, welcome to the forum 
The steps should be very similar, for both windows and linux.
Regarding SFTP specifically, recent versions of windows have native ssh support. I found this documentation with a quick search for “windows ssh config”: OpenSSH Server configuration for Windows | Microsoft Learn
I didn’t look too far into the documentation, but it seems the config file location should be:
%userprofile%\.ssh\config, which seems to be the equivalent to ~/.ssh/config on linux.