Of course tetrapak cartons aren't plastic free. There are usually 6 layers glued together: polyethylene, paperboard, polyethylene, aluminum foil, polyethylene and polyethylene.
They are on average made of paperboard (70%), aluminium (5%), and polyethylene plastic (25%).
And most have a plastic lid.
They are still not completely recyclable.
The polyethylene is the same as (most) plastic bottles.
If you use a milk substitute (such as soya, almond or oat milk it comes in something. Usually tetrapack - unless you make it yourself or buy in glass (say, from the milkman).
Not critical here. Just saying.
Very little is simple.