I had a pretty rocky experience upgrading Duplicati from 2.3.0.4 to 2.4.0.1, so I wanted to share what happened and offer suggestions on how it could be improved.
Prior to the upgrade, I used a preload.json file in C:\ProgramData\Duplicati\ to configure the secret provider and settings encryption key (as I detailed in this post).
After installing 2.4.0.1, Duplicati would not start, crashing at startup with a very long error message. Unfortunately, when I tried to copy the text from the error dialog to the clipboard to examine it further (highlighting the text and pressing Ctrl+C), the dialog would immediately close without writing anything to the clipboard.
Suggestion #1
Add support for copying the text of the error directly from the TrayIcon crash dialog box.
Eventually, I found the Duplicati.GUI.TrayIcon-crashlog.txt file and determined that a Duplicati.Library.Interface.SettingsEncryptionKeyMissingException was being thrown. I was confused as to how this could be the case, as I had not changed anything to do with the encryption key, secret provider, or preload file during the upgrade.
I spent a while double-checking that the secret was still in the Windows Credential Manager, that the secret name was correct in the preload file, that Duplicati was starting as the correct user, etc.
Finally, I went to read the preload settings documentation to see if I was somehow missing something and, sure enough, there was a note that C:\ProgramData\Duplicati\preload.json was no longer supported as a valid preload file location. After I moved the preload file to a supported location (Duplicati’s installation folder, in my case), Duplicati started up normally.
Suggestion #2
Duplicati should detect and warn the user of preload settings files in deprecated locations, rather than silently ignoring them.
Sorry for the wall of text; if y’all have any questions for me, I’d be happy to answer them.