3.97.1 (unstable):
Distro packagers should probably not package this yet.
See https://mail.gnome.org/archives/gtkmm-list/2020-January/msg00009.html

Gtkmm 3.97.1 is a C++ binding of gtk 3.98.0.

Apart from the changes listed below there are lots of small changes.
Most changes correspond to similar changes in gtk4.

Gdk:

Gtk:
* Add Text
  (Kjell Ahlstedt)
* Builder: Add returning versions of get_widget[_derived]
  Add get_object<Derived>(name) overloads
  (Daniel Boles) Issue #43, merge request !11
* Builder: Remove old get_widget*() overloads
  (Daniel Boles) Merge request !17
* MenuButton derives from Widget (was ToggleButton)
  Add the Native interface
  Rename GestureMultiPress to GestureClick
  (Kjell Ahlstedt)
* Add Gtk::Constraint, Gtk::ConstraintGuide, Gtk::ConstraintLayout,
  Gtk::ConstraintTarget
  (Kjell Ahlstedt)
* Fix ownership of some GLists
  (Kjell Ahlstedt)
* Add CenterLayout and NoSelection
  (Kjell Ahlstedt)
* Update class hierarchy of AppChooserButton, InfoBar, SrtakcSidebar,
  StackSwitcher
  (Kjell Ahlstedt)
* Add Gtk::Window::unset_titlebar()
  (Kjell Ahlstedt) Issue #57 (Daniel Boles)
* Gtk::Application, Window: Always remove a window from its app when hidden
  (Kjell Ahlstedt) Issue #56 (Daniel Boles)
* Remove ModelButton
  Builder: The gtkmm__ prefix must sometimes (but rarely) be used in
  the .ui file. See the description of get_widget_derived().
  (Kjell Ahlstedt)
* Remove CheckMenuItem, Menu, MenuBar, MenuItem, MenuShell,
  RadioMenuItem, SeparatorMenuItem.
  Add Gtk::PopoverMenuBar, replaces the removed MenuBar
  (Kjell Ahlstedt)
* Remove old drag-and-drop API.
  Add Gtk::DragSource, DropTarget.
  (Kjell Ahlstedt)
* Remove WidgetPath
  Rename IconInfo to IconPaintable
  (Kjell Ahlstedt)
* Remove MenuToolButton, RadioToolButton, SeparatorToolItem,
  ToggleToolButton, Toolbar, ToolButton, ToolItem, ToolShell.
  Use Box instead of Toolbar, Button instead of ToolButton, etc.
  Add Gtk::EmojiChooser
  (Kjell Ahlstedt)

Demos, tests:
* Update many demo programs and test programs.
  (Kjell Ahlstedt, Daniel Boles)

Documentation:
* Gtk::TreeView::append_column() doc: Add code example
  (Pavlo Solntsev) Merge request !21
* Many improvements
  (Kjell Ahlstedt, Daniel Boles)

Build:
* Merge libgdkmm-4.0 and libgtkmm-4.0 into one library.
  (Kjell Ahlstedt) Issue #48
* Visual Studio Build: Build gdkmm into gtkmm
  (Chun-wei Fan) Merge request !20
* Use glibmm-2.64 instead of glibmm-2.62
  Require gtk4 >= 3.98.0
  (Kjell Ahlstedt)