The diy video has the right idea. But twisty light gauge aluminum is the wrong material to use. Instead, use large diameter plumbing drainage pipes with tight fittings.

The downspout should be directed into a 3" or 4" PVC or ABS wye fitting above grade. This provides a cleanout point should you ever need it.

At the end of the run, you use a "popup". It stays closed until there's water flow, then closes when the water stops flowing. This deters critters from taking residence in your drains.

The corrugated pipes you're using should be those that have a sleeve around them to resist plant roots attracted to the water.

To help with drainage, I rest the pipes on a bed of free-flowing gravel. No fines.

I installed hard and corrugated downspout drainage all round for our last home that we had six years. This is a cold climate and there were no problems. I did notice that some of the unsleeved corrugated lines we dug up for a pool were infiltrated by shrubbery roots. I've use similar drainage at corners of a couple of homes I've built since, also with no problems reported. I often see new homes where the builders dump the downspouts onto driveways, which turn into sheets of deadly ice in the winter. Underground drainage is a cheap safe alternative.

The only odd side effect I noticed was that the grass around the drainage lines was much lusher and healthier than the rest of our lawn. (But, then, I'm not much of a gardener.)

Thanks for the feedback Worthy.

Encouraging to hear that freezing should not be a problem.

"...unsleeved corrugated lines we dug up for a pool were infiltrated by shrubbery roots."

Yes, when I do my house I will use a "sock" designed to keep the fines, and hopefully roots, out of the perforated pipe.