@ts678 pointed me here since I was wrangling with Ubuntu 24.04 (released last week).
Just downloaded and apt installed the gui.deb version on a fresh Ubuntu 24.04 in a VM with these results, dependency error for libicu72, the correct version is probably libicu74.
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Note, selecting 'duplicati' instead of './duplicati-2.0.8.105_debug_2024-04-16-linux-x64-gui.deb'
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
duplicati : Depends: libicu but it is not installable or
libicu72 but it is not installable or
libicu71 but it is not installable or
libicu70 but it is not installable or
libicu69 but it is not installable or
libicu68 but it is not installable or
libicu67 but it is not installable or
libicu66 but it is not installable or
libicu65 but it is not installable or
libicu63 but it is not installable or
libicu60 but it is not installable or
libicu57 but it is not installable or
libicu55 but it is not installable or
libicu52 but it is not installable
E: Unable to correct problems, you have held broken packages.
The libicu library for Ubuntu 24.04 seems to be libicu74. So adding that dependency should fix this.
I was using same technique as described yesterday to create a modified .deb for further tests. This didn’t work (no control.tar.gz in archive).
Had to stop for now, just wanted to report the error. Might do some more digging later.