Development news: thanks to Massimo and Nikc contributions, the next #development version (2.99.14, the branch which will end up in stable GIMP 3.0) of #GIMP will have an outline feature in text layers.

You will be able to choose the outline color, or even a pattern, outline width, outline antialiasing and the line style (if you want a dash pattern rather than continuous lines and so on). It's pretty featureful.