Heat fruits in a small pot over medium-high heat, stirring occasionally, until the fruits begin to break down, about 10 minutes.
Use a wooden spoon to mash the fruit to your desired consistency.
Stir in the chia seeds, lemon juice, and sweetener until combined.
Remove from heat and let cool for 5 minutes.
The jam will thicken as it cools.
Serve immediately, or transfer the jam to a sealed container and refrigerate it for up to 1 week, or freeze it for up to 3 months.