Since ggtern doesn't seem to get maintained anymore*, are there any alternatives to produce ternary diagrams with ggplot2?
*the current Version of ggtern (3.3.0) was released over a year ago, and it breaks ggplot2 Version 3.3.0 and up. Since there were a lot of changes from the previous ggplot2 versions, the only workaround (that I know of...) is to use an older Version of ggplot2 (i.e. Version 3.2.1)