Everything I saw in tutorials has a little button you click to choose the font style, but I do not see one.
That looks like the pop-up quick toolbar that appears over the selected area. There should be a "Tool Options" tab in one of the floating toolboxes (mine is on the bottom-left side of the screen by default) that has additional options when the Text tool is selected. If it's not there you can add it to a toolbox through the little left-pointing triangle on the tab bar.
The pop-up text editing tool doesn't have the right functionality, so you would appear to need the default docked window for the above solutions to work.
Here's the method to restore it (if it's AWOL):
Edit > Preferences > Window Management > Reset Saved Window Positions to Default Values [src]
Then X out of GIMP and reopen, and the other solutions should work at that point.