Wishing to pull homey devices into Homey.
The first rule of home automation applies: “the model number matters.”
If you can list specific models, we can answer better. They use some of the same protocols, so there should be some that work with either hub.
That said, being able to work with either is not the same as being able to work with both simultaneously, so for many devices you have to choose. If it’s connected to a Homey hub it can’t also be connected to a SmartThings hub and vice versa. But again, the model number matters. Some devices like a Hue bridge might be able to show up in both apps at the same time.
If you did want to leave the devices connected to a Homey hub but also use them with a SmartThings account, you could get partial integration by using IFTTT as an intermediary. But you might have to use virtual devices as proxies on the ST side, which could be a lot of setup work. And there’s also the potential for the device status to get out of synch.