Another thing you can do is select the text that you want to outline, and then in the box on the right, right click the layer and choose alpha to selection, then go to selection tool in the top left, and choose grow, grow it by a few pixels, and then use the paint tool to in-paint a larger border for the text on a layer behind the text itself.

I stopped updating GIMP after 2.10 broke my workflow with changes to how it handles colorspace and alpha.