In a large skillet over medium-high heat, add the olive oil. Add the sausages and cook, turning occasionally, until they are evenly browned and fully cooked, about 12 minutes. Once done, transfer the sausages to a plate and set aside.
Add the sliced red onion to the skillet and sauté, stirring frequently, for about 5 minutes, or until the onion softens.
Stir in the Swiss chard stems and continue cooking for another 7 minutes, until the onion becomes golden and the stems are nearly tender.
Add the rhubarb slices, dried currants, maple syrup, garam masala, kosher salt, grated ginger, and bay leaf to the skillet. Stir well and cook for 7–10 minutes, stirring often, until the rhubarb softens into a thick, chutney-like consistency and the chard stems become tender. If the mixture starts to stick or burn, add a few tablespoons of water to the pan as needed.
Toss in the torn Swiss chard leaves and stir them into the mixture. Allow them to cook for about 5 minutes, or until they are wilted and softened. Once done, remove the bay leaf and transfer the chard mixture to a serving platter.
Return the sausages to the skillet and heat them for 2 minutes, gently shaking the pan to re-crisp the sausages and ensure they are hot all the way through.
Plate the sausages over the chard-rhubarb mixture and serve immediately.