Android 7 and saving torrents directky to usb-devices

[Orange Marmelade]

As per these instructions:
https://forum.xda-developers.com/android/general/write-data-to-external-sd-card-kitkat-t3248220

I'm trying to use my attached usb-stick as download destination for torrents usng a torrentclient like Flud.

I connected a 64gb usb to my Android 7 device. Let it detect it and it's attached fine. I created the homedirectory of torrent-software Flud on my usbstick. Android/data/com.delphicoder/flud/files.
I cannot see it in the dropdown menu in Flud, to choose as download destination. Why won't it work?!?