Probably, though external frame packs mostly don’t exist any more. At least not in the normal consumer outdoor gear market (REI, etc).

A fair chunk of the UL market forgoes a frame completely, and just uses some foam to add rigidity and padding. That’s usually for people going with a truly minimal base weight… Tarp tent, minimal quilt, possibly no stove (living off overnight oats and other things that can be consumed after soaking).

Interesting. It's been so long since I've looked into this stuff that I didn't realize external frame packs were mostly gone.

And that gets even more interesting as many Deuter backpacks are hybrids, with a rigid frame that leaves a cooling air pocket between your back and the pack, while looking like a non-frame backpack.

Somehow I didn't realize that Deuter is a backpack manufacturer.