I eat massive amounts of store-bought lingonberry jam, especially in my breakfast cereal or porridge.
The best variety is uncooked that you make yourself, however. With fresh berries: mix half the amount of granulated sugar and then stir, stir, stir until all the sugar granules have dissolved in juice formed from the berries that have got mashed. With frozen berries you don't have to use as much sugar.
The berries grow wild where I live but not in very large amounts so I buy it.
I also cook orange marmalade and rhubarb-ginger marmalade every year when the respective ingredients are in season. I vary what types of oranges I use but it is usually half Seville oranges. Peel is only from organic oranges with the white cut off.
When cooking marmalade I use a "Jam sugar" that contains pectin and preservatives so I don't have to mix that in.