Almost all were shipped using recycled boxes and packaging material (minus tape).

You know, they sell recycled tape. They have cellulose tape, but I personally would suggest paper based tape. It's a little harder to use until you get used to it, because you use water to stick it on, but it actually seals better than normal tape, because it bonds with the cardboard of the box.

I personally like EcoEnclose. (Not sponsored.) They even give away free samples of their packing materials, which are all either at least partially recycled, or compostable, or both.

You can get paper tape from all sorts of places though. It's just hard to get in many normal consumer level stores, because they suck. Lots of it is made from recycled paper, just because.