Line a rimmed baking sheet (about 9x13 inches) with parchment paper. Make sure it fits flat in your freezer.
In a medium bowl, whisk the yogurt, sweetener, vanilla, and pinch of salt until smooth.
If using, whisk in heavy cream or coconut cream for a silkier texture.
Taste the mixture. Adjust sweetness now—frozen foods taste less sweet, so it should be slightly sweeter than you want the final bark to be.
Spread the yogurt mixture onto the prepared sheet in an even layer, about 1/4-inch thick. Thinner layers freeze faster and snap better.
Scatter the berries evenly over the top. If using strawberries, chop them small so they freeze uniformly.
Sprinkle on nuts, seeds, coconut, and chocolate if using.
Lightly press the toppings into the yogurt so they stick.
Add lemon zest over the top if you like a brighter flavor.
Freeze, uncovered, for 2–4 hours or until completely firm.
Once solid, lift the bark using the parchment and break it into pieces. For cleaner edges, you can slice it with a sharp knife.
Store pieces in a freezer-safe container or zip-top bag with parchment between layers to prevent sticking.