gtkTtk VS pstk

Ideally, something like gtkTtk that has GTK do the actual drawing would be integrated into Tcl/Tk and become the default on Linux. In the meantime, there are third party themes that imitate the look and feel of the most popular GTK and Qt themes. I use MATE with the Arc GTK theme, so I went with the Arc theme. There was even a Debian package for it (sudo apt install tcl-ttkthemes). We can then apply the theme system wide (echo '*TkTheme: arc' | xrdb -merge -), so that all Tk apps such as git-gui also inherit the theme. It is probably better to give your Linux users instructions on how to install their own theme instead of hard coding one with ttk/set-theme, so they can choose one that matches their system theme (KDE users might pick Breeze while Ubuntu users might opt for Yaru). The screenshots in this tutorial use the Arc theme.

All PS/Tk function names begin with tk/ or tk- (or ttk/ and ttk- for the few Ttk-specific functions). The doc directory in the PS/Tk GitHub repo unfortunately has not been updated since this convention was adopted. One example from the docs is start-tk which is now tk-start.