Seeing “line 0, position 0” makes me wonder if Duplicati detects and errors specially if it gets nothing at all, or if this is what it says. Though symptoms were different, this was thought to be from Docker network changes.
@zlatovlas is reporting that Windows Beta fails, but Canary works. I’m not sure what @RobHofmann runs, but there’s been a wish for a newer Beta, and the recent 2.0.3.11 seems to be pushing closer than before…
For issues that look like they might be connection-related, using the “Test connection” button is a purer test.
Dropbox has Windows and Linux clients, although possibly you don’t want the disk/network/risk add it brings.