I’m not seeing anything obvious from this side, are you sure there’s no access from the inside?
If not I would guess that you need to remove the strips from around the edges, similarly to deglazing a window.
Judging from the age of the surrounding hardware you’re going to be lucky if you find fluorescent tubes and an old “magnetic” ballast. Consider changing that out for some LED strip lights, it will be similar in cost and last much longer.