That he doesn’t react to the suggestion of trying daily a few hours of cardio exercises instead preferring a few hours of insomnia, indeed tells me there are other issues in his/her life.

That's because every person who struggles with sleep has heard this advice a thousand times. It just doesn't work for all of us.

I lift weights, and I make sure to do big muscle groups. I wake up around the same time every day, ish. I do not drink coffee in the afternoon. I do not use blue light screens at night. And any number of other advice that people keep bringing up.

Like the comment above that says if you wake up at 06, you will be tired at 23. Yeah, sure, but you still won't be able to sleep. All that does is make you more tired permanently, but sleep still doesn't happen.

People just do not work the same, some people are really more active at night. And this advice is echoed constantly whenever this topic is brought up.

For what it's worth as one bit of advice: Try to make the best of what you can do in those long deep night hours. If you can't use them for sleep, as a deep night owl, then make them count for something else that's useful. Many of history's most interesting, famous and also infamous characters (and overall very productive people by sheer virtue of their achievements) were extreme night owls. It didn't stop them from creating and working. For certain types of endeavor or work in particular, the part of the day in which the hours are put in isn't nearly so relevant as the hours simply being used in the first place.

Just a few observations from one night owl to another; I can rarely go to sleep before 4 am.

No, it's because if you have an actual medical condition, doing exercise doesn't work. I do exercise daily, it doesn't actually solve the core issue. It's like saying you can solve a broken leg with exercise.