To run CumulusMX with my weather station, I need to install an old version of Mono (version 126.96.36.199) as the lasts versions are not compatible.
It is ok with my RPi3b Stretch. Procedure is :
1. Create the file /etc/apt/sources.list.d/mono-xamarin.list with the line
deb http://download.mono-project.com/repo/debian wheezy/snapshots/4.0.5 main
2. sudo apt-get update
3. Install the compatible version of Mono: sudo aptitude install mono-complete=188.8.131.52-0xamarin1
But with my new RPi4 Buster, there is an error message on step 2 alerting that this deposit is not signed.
Step 3 thus cannot be completed.
How can I fix it ?