I will not be porting Gaupol to GTK 4. While I do like a lot of the additions in the toolkit and the direction of core GNOME, the extent of changes is unbearable for any bigger hobby project. This has become apparent while porting a smaller project to GTK 4. Smaller fixes and basic maintenance will continue as thus far. Not porting to GTK 4 is not any immediate issue, I expect GTK 3 to be available for quite a while still.

For anyone interested in continuing the work in some form, I'd recommend considering starting from scratch. Firstly, Gaupol was started in 2005 using GTK 2 and Python 2, and also was a learning project for me so it's to an extent both dated and suffering from bad design. Secondly, the Gtk.TreeView widget and associated cell renderers etc. used very extensively in Gaupol are deprecated and due to be removed in GTK 5, so a major UI rewrite would be needed at that point anyway.