Choose a deodorant in a cardboard push-up tube, a glass jar, or a refillable metal case that takes cardboard refills.
A plastic deodorant stick weighs about 30 g; six a year is 180 g. Lush and similar brands sell naked or paper-packaged versions, part of the naked-product shift that has avoided thousands of tonnes of plastic.
The catch: natural deodorants without aluminium salts work differently from antiperspirants; expect a short adjustment period, and check that refill cartridges are cardboard rather than plastic.