It’s light on exploration and close to a visual novel, but for non-linear narrative, it’s possible you might like 13 Sentinels: Aegis Rim.

I don’t want to say too much about it, but Undertale is more about a different kind of loop structure, something unique to gaming. If you like it, you may also like Pony Island, which does work with loops a bit.

Chrono Trigger’s time travel works more like crossing timelines that are in parallel but are also in motion, all with some impact on each other. Still a great game in general, though.