Rain water harvesting -- square metal downspout

Hello all,
I have 2, 55 gallon barrels that i would like to fill located next to a 4 " square metal down spout.

I am not seeing any adapters for it.

Might it be better to switch over to 4" round pvc?

Going from downspout to barrel, can you move water from downspout to top of the rainbarrel or side?

I am sure other folks have a better answer.

What I would do is cut the downspout above the barrel.  Use the existing fittings as shown in picture to allow the flow to go into a hole cut in the top of the barrel.

Are you going to use a pump to pump water out of the barrel or add a spigot at the bottom to use a garden hose?

I think Anne is on the right track. Eavestroughs and downspouts are notoriously non-standard. I often modify square / rectangular tube with an open notch at the end to interface with ... anything. Or I will add temporary open eavestroughs that I have scrounged.

These are perfectly functional and free solutions, but not exactly neat-and-tidy from an aesthetics point of view. There's a fair bit of Heath Robinson / Rube Goldberg in my water catchment systems.