Existem outras duas boas opções para adicionar ao Centro de Software e ao Gerenciador de Pacotes Synaptic:
1. Usando o 'apt-cache search'
Você pode abrir um Terminal e procurar por todos os arquivos -dev anexados ao libgtk da seguinte forma:
andrew@athens:~$ apt-cache search libgtk | grep dev
libgtksourceview-3.0-dev - development files for the GTK+ syntax highlighting widget
libgtkspell-dev - Development files for GtkSpell
libgtkspell3-3-dev - Development files for GtkSpell
libgtk-3-dev - development files for the GTK+ library
libgtk2.0-cil-dev - CLI binding for the GTK+ toolkit 2.12
libgtk2.0-dev - development files for the GTK+ library
libgtkmm-2.4-dev - C++ wrappers for GTK+ (development files)
libgtkmm-3.0-dev - C++ wrappers for GTK+ (development files)
libgtk-sharp-beans2.0-cil-dev - Supplementary CLI bindings for GTK 2.14+ - development package
libgtk-vnc-1.0-dev - VNC viewer widget for GTK+2 (development files)
libgtk-vnc-2.0-dev - VNC viewer widget for GTK+3 (development files)
libgtkada-bin - Ada binding for the GTK+ GUI (development utilities)
libgtkada2.24.4-dev - Ada binding for the GTK+ GUI (development files)
libgtkdatabox-0.9.2-0-dev - Gtk+ library to display large amounts of numerical data (development)
libgtkdataboxmm-dev - C++ bindings for GtkDatabox - development files
libgtkglada2.24.4-dev - Ada binding for GTK+ OpenGL extensions (development files)
libgtkglext1-dev - OpenGL Extension to GTK+ (development files)
libgtkglextmm-x11-1.2-dev - C++ bindings for GtkGLExt (Development files)
libgtkhex-3-dev - GNOME Hex editor for files (development headers)
libgtkhotkey-dev - Gtk hotkey static libraries and headers
libgtkimageview-dev - image viewer widget for GTK+ (development files)
libgtkmathview-dev - rendering engine for MathML documents
libgtkpod-dev - main library for the gtkpod package, development kit
libgtksourceview2.0-dev - development files for the GTK+ syntax highlighting widget
libgtksourceviewmm-3.0-dev - C++ binding of GtkSourceView - development files
liblablgtkmathview-ocaml-dev - OCaml bindings for libgtkmathview, a GTK widget to render MathML
liblablgtksourceview2-ocaml-dev - OCaml bindings for libgtksourceview2, a source editor GTK+ widget
libgtk-dotnet3.0-cil-dev - GTK.NET library - development files
libgtk3.0-cil-dev - CLI binding for the GTK+ toolkit 3.0
libgtkextra-dev - development files for libgtkextra-x11-3.0
libgtkgl2.0-dev - OpenGL context support for GTK+ (development files)
libgtkspellmm-3.0-dev - C++ wrapper library for GtkSpell (development files)
andrew@athens:~$
As variações deste tipo de pesquisa são limitadas apenas pelo seu conhecimento de expressões regulares:).
2. Use a Web ...
Frequentemente, utilizo aqui a muito interessante pesquisa baseada na web:
Pesquisa de pacotes do Ubuntu no link
Existem muitas, muitas possibilidades em uso para procurar pelo Ubuntu Release, nome do pacote, nomes de arquivos, etc. etc. Uma busca simples por libgtk sob Xenial pode ser visto aqui ...
Várias outras possibilidades, mas esperamos que você comece ...