Agony - I agree pretty much with the last two Kitchen Goddesses
Jam/jelly recipes from Australia's acknowledged Gurus (Country Women's Association et al) are never processed in a water bath.
I recycle used glass jars from store-bought pickles, mayo, olives etc. provided they have an acid-resistant lid. I remove labels and glue and wash jars and lids on hottest cycle of dishwasher. Store empty jars, lids on, until ready for use.
No need for special jars, seals, clips.
While jam or jelly is reaching setting point, take lids off jars and heat both in an oven about 100degC. for just a few minutes.
Pour hot jam into hot jars and seal immediately. Turn upside -down for a few minutes if you wish. I am confident this will keep in a dark cupboard for a minimum of one year.
I always add strained lemon juice, at least 1 lemon per kg of fruit, so very rarely need pectin to obtain a set.
I had never heard of freezer jam until your post!