libgtksourceviewmm-3.0-dev binary package in Ubuntu Focal arm64

 GtkSourceViewMM is a C++ binding of GtkSourceView, an extension to
 the text widget included in GTK+ 3.x adding syntax highlighting and
 other features typical for a source file editor.
 .
 GtkSourceViewMM is crafted to integrate well into applications using
 the gtkmm framework.
 .
 These are the development files for libgtksourceviewmm, needed only
 if you wish to write or compile software which uses it.

Source package