Combine the berries, lemon zest, lemon juice, and maple syrup in a medium saucepan. Bring to a boil, then reduce the heat to a lively simmer. Cook, stirring occasionally, until reduced by about half and the jam coats the back of a spoon, 12 to 16 minutes for fresh berries and 22 to 26 minutes for frozen ones.

Add the chia seeds and cook until the seeds become gelatinous, about 1 minute. Some berries will remain whole after cooking. Remove the jam from the heat and let cool completely. It will thicken as it cools, but you can enjoy it right away as a topping for toast or mixed into oatmeal or plain yogurt.

To store, transfer to an airtight container and refrigerate for up to 2 weeks or freeze for up to 3 months.