The function "Do not scan these folders:" doesn't work on 1.21 version.
Confirming that on freshly updated Arch Linux. I have two volumes, which are mounted in /run/media/myusername, and both of them are scanned when I choose to scan / , and this happens regardless of whether I select any of these paths to not to scan: /run, /run/, /run/media, /run/media/, /run/media/myusername, /run/media/myusername/, /run/media/myusername/vol1, /run/media/myusername/vol1/, /run/media/myusername/vol2, /run/media/myusername/vol2/.
this should be fixed by by Joachim with commit b06ec65e0c79d8eea8e44d4367364fd572c3dd19.