Deluge
On Unraid 6.9.2 running binhex-delugevpn.
Works great but was having an issue setting up thin client.
Kept receiving "Username does not exist". I had followed deluge thin client setup guide and auth was created at ~/.config/deluge. Added users to auth file, still no dice. Searched container directory structure for any other instances of the auth file. It was no where else.
After not finding anything online, I signed into UNRAID console and navigated to the /mnt/user/appdata/binhex-delugevpn and searched for the auth file. It was at the path /mnt/user/appdata/binhex-delugevpn/auth. I modified this auth file, adding users, and this enabled the thin client access.
Hope this helps anyone having a similar issue.
Unraid deluge thin client fix for "USERNAME does not exist"
Re: Unraid deluge thin client fix for "USERNAME does not exist"
This solved it for me, 2.5 years later 
To save people from doing the same mistake as me, I wanted to add that you need to add authentication level to your user, otherwise you will be able to connect, but no torrents will be displayed.
username:password:authentication level - so for an admin account that would be username:password:10
https://deluge-torrent.org/userguide/authentication/
Sorry for the necro, but this was the top result when I searched.
To save people from doing the same mistake as me, I wanted to add that you need to add authentication level to your user, otherwise you will be able to connect, but no torrents will be displayed.
username:password:authentication level - so for an admin account that would be username:password:10
https://deluge-torrent.org/userguide/authentication/
Sorry for the necro, but this was the top result when I searched.