I recommend lifting weights, but any physical activity will do. The key is to exhaust yourself...using an elliptical for 30 minutes won’t work.
I've read advice like this a lot, but it seems like such a difficult thing to jump into, especially if I've not had much success with small trials (i.e. the 20 mile bike rides). It also makes me wonder what the intended end goal is; if I spend all of my time exercising, and that does end up fixing me, what do I go back to?
The idea isn’t so much to get tired once and then recover, but to consistently push your body so that you are tired and sleep well. This means lifting weights 3/4 times a week, running HIIT, rowing, etc. Not just a long bike ride for a few hours. It’s not something that will fix your issues overnight.
A more balanced lifestyle, hopefully.
I've had sleep troubles as well over the years and also started biking to stay healthier. For me personally, the more regularly I exercise, the better I sleep. Thanks to modern technology, I discovered that regular exercise lowered my resting heart rate. The lower my heart rate at night, the better I sleep.