I wouldn't worry about the plastic liner, TBH. Afaik this plastic lining is burned off/removed when recycling the aluminum. Unlike plastic, and like steel, aluminum is very economical to recycle, so it mostly is and has been for decades.
Aluminium its not economical to recycle at all. It takes a lot of energy to recycle it, which is done only because processing bauxites is even more expensive.
Do you think burning plastic is an environmentally sound practice?
That depends on how complete the combustion is and how well the produced gasses are filtered.