Tried the suggestions from this post on this forum. And only installed mono-devel. This resulted in the following error:
sudo apt install ./duplicati_2.0.7.1-1_all.deb
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Note, selecting 'duplicati' instead of './duplicati_2.0.7.1-1_all.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: libappindicator0.1-cil but it is not installable or
libappindicator3-0.1-cil but it is not installable or
libayatana-appindicator1 but it is not installable
E: Unable to correct problems, you have held broken packages.
I’ve made a VM with a snapshot, so testing with with risky suggestions shouldn’t be a problem.