It sounds like you’re running into the same thing as mentioned here:
Unlike Windows, Linux is very generous in what it allows in file / path names.
I dabble with Linux, so I might be wrong, but I believe you can escape certain characters with a \ backslash, so you if you care to play around you could try something like cd WORKGROUP\;routeruser\@tplinkwifi.net. Not that it will help anything, but you might learn a little more about the Linux CLI.
When running Duplicati in Windows, a samba share can be access just by the normal UNC path (e.g. //WORKGROUP/volume(sda2)/Duplicati) however on Linux you would need to mount that share to a mount point then use that “local” mountpoint as your destination.
As a slightly-more-than-newbie Linux user, I would assume this means you either have to have that moutpoint always connected or you MIGHT be able to mount and unmount in --run-script-before-required and --run-script-after scripts, though to do it “right” you would likely want to verify it’s not already mounted before mounting and that it IS mounted before unmounting.
Note that there is an older Github ticket about this, along with some comments about potentially adding a CIFS client to Duplicati. Maybe adding a bounty to this might help it come about more quickly!
