How I do it: Make text, create a new background layer, make the same text but slightly bigger in the colour you want your outline to be, align background text as needed. Save as .png and import into new image if you're looking to add the outlined text to somewhere else (though I suppose you can just merge layers, I do my crap in fits and spurts so I often prefer having the little pieces as discrete files so it's easier to come back to it. Also I've fucked up and merged when I probably shouldn't have a LOT).

Takes some futzing about for sure but that's part of the fun for me.

Edit: Super shitty outline done just by doing the same font size bolded in black. Can obviously be done much better but you'll get the idea.

I haven't found a way to directly add an outline frame to the text but you can go to tools->shapes and set it to outline no fill and manually do frame the text

The interface is a bit strange at first but it is a genuine multiple layer image editor it is great.

A tip, make sure to confirm/complete a tool's action before you switch to a different one, it is easy to switch off a tool while it is still "previewing" something.