Possibly you have some leftover update as described here, however you need the CLI version of the test. Below might be equivalent (translate to Linux CLI command use, etc.). Key question is “Current Version”. You might have an update that’s not affected by uninstalling/reinstalling but is being invoked and crashing.
The “Current Version folder” on this system is a slightly modified 2.0.4.5. That’s not a normal folder name. Here the Program Files version is actually 2.0.3.12. Read changelog.txt if you’re unsure of what you have.
C:\Program Files\Duplicati 2>Duplicati.CommandLine.exe system-info
Duplicati: Duplicati.CommandLine, Version=2.0.4.5, Culture=neutral, PublicKeyToken=null (Duplicati.Library.Main, Version=2.0.4.5, Culture=neutral, PublicKeyToken=null)
Autoupdate urls: https://updates.duplicati.com/beta/latest.manifest;https://alt.updates.duplicati.com/beta/latest.manifest
Update folder: C:\ProgramData\Duplicati\updates
Base install folder: C:\Program Files\Duplicati 2
Version name: "2.0.4.5_beta_2018-11-28" (2.0.4.5)
Current Version folder C:\ProgramData\Duplicati\updates\2.0.4.5 beta