I have three Pi's, a 2B running Moode 4, a 3B running Nginx as a proxy sever under stretch for my home network and a 3b which is mainly runnining CumulusMX under jessie via mono for my weather station and website (www.craythorneweather.info).
I would like to upgrade the jessie Pi3 to stretch but unfortunately, when I try, the latest version of mono ( 5.xx.x)which is automatically installed on the upgrade is incompatable with CumulusMX and CumulusMX is unlikely to be further developed to take account of changes in mono.
I have tried to uninstall mono and reinstall an earlier version (4.xx.x) but that too is incompatible with CumulusMX and I am not sure that the instructions I have used, copied from various places on the web, are that current or comprehensive.
The version of mono that does work under jessie is 3.2.8. If anyone can help me with instuctions that would completely uninstall mono from stretch and reinstall mono 3.2.8 from an archive I would be most grateful.