There definitely is a mechanism: “Matter bridges.” They don’t connect two platforms together, but they do allow the same device to be used with two different platforms at the same time. It’s basically the same architecture as the pre-matter hue bridge. You can have a hue bridge connected to Alexa, smartthings, HomeKit, and multiple other home automation platforms all at the same time, and the bridge will bring along a number of its attached devices, although not all models or all features. Matter bridges work pretty much the same way.
For example, you can connect aqara devices to their own Aqara M2 hub and then connect that hub to smartthings as a “matter bridge“ and it brings along some of the devices. You can then create rules, either in the SmartThings app, or in the aqara app, whichever works better for you. ( that said, smartthings has already said that it does not plan to make any of its hubs, a “Matter bridge“ so it is only supporting matter one way in, but not out.)
But I was referring to whether an individual device like a smart plug would be individually certified for Wi-Fi over matter or thread over matter. That’s when the individual device can display the matter logo. If it’s done that way, instead of via a matter bridge, you’ll definitely be able to add the individual device to smartthings. That’s the definition of the logo.
Like this plug:
https://www.amazon.com/TP-Link-Tapo-Supported-P125M-3-Pack/dp/B0BNWGZ545/?th=1
See the following:
FAQ: What do I need to add a Matter device to the SmartThings app? Do I need a bridge router device?