Long story short: the smartthings platform introduces some issues that you don’t find in other certified zwave and Zigbee controllers. And then the cloud architecture adds some issues on top of that.
In smartthings, every device has a “DTH“ (device type Handler), which is essentially like a printer driver. It takes the messages that the platform wants to send to the device and converts them to the exact format that the device is expecting. And the same thing coming back the other way.
Smartthings provides a bunch of “stock“ DTHs, including some lowest common denominator generic ones, and those work quite well for simple devices, like an on/off switch.
However, as soon as you start getting into advanced features or even just multi Button devices, the stock DTHs may not work. So then you have to get into “custom code“ which just means somebody wrote something for it other than what is provided by smartthings. This might be the manufacturer, another community member, someone who sells access to their code, or you yourself.
Up until 2020, the process for creating and using custom code was pretty simple, because smartthings let any customer upload custom code to the smartthings cloud and run it from there. All for free.
However, this did lead to some unreliability because occasionally runaway code would start to eat up all the common resources. 
So for this and some other reasons Samsung is changing their entire architecture. They’ve published their API so that now device manufacturers or other developers can host their own custom code and connect with smartthings via a cloud to cloud integration, sort of similar to how IFTTT works.
manufacturers who go through a certification process can get these integrations listed right in the app, and those are the ones that you will see you when you open app and go to add a new device and choose by brand.
Individual developers can also create these for themselves, usually MQTT for the integration. And we are starting to see more Brands doing this.
However, this doesn’t help with Z wave or zigbee devices, which have to be able to communicate with the hub directly even if you are using a custom DTH. These are now called “hub connected devices“ but smartthings has not yet published details on how any of this will work in the future. So a lot of the individual developers have stopped writing new custom code for now, because they don’t want to have to rewrite all of it once the new architecture is complete.
And most of the zigbee and zwave device manufacturers aren’t doing anything that is smartthings specific, either: their usual response is “we produce certified Zigbee Devices that work with the standard independent protocol, any platform specific issues are left up to the platform.”
Which would be OK, except that Smartthings has already indicated they don’t want to be responsible for those custom integrations, so it’s kind of in a no man’s land for now. Especially since there aren’t any published details on how it’s all going to work anyway.
So… if this was 2019, my response would be “smartthings doesn’t always handle multi endpoint devices well, but we may be able to get something going with custom code.” And then there would very likely be two or three community members who would be interested in it as a project and start some work. And you might end up with a workable DTH (like Adam’s for the Z wave version) or you might end up with the answer that it’s just not going to work with smartthings, but at least you would know.
Now, though, most people just don’t want to invest that time in something that may change at any moment. So there’s a lot less custom code being contributed in the community these days.
All of which is to say… Let’s hope that somebody who knows more will see your topic title and chime in to say what’s currently available. But while writing custom code is possible on the smartthings platform, The fact that we’re at this transition moment means that most people just don’t want to do it for a zigbee device right now.
I do know that in the past there were two or three different community members who tried to get this specific device working and were not able to because of some timeout issues with the smartthings cloud architecture. I just don’t know if that would still apply.
Wall-mount Zigbee multi-button controller (Sunricher, iCasa, etc.)
I’m going to tag @johnconstantelo just because I know he’s been doing a lot with Zigbee devices and he may have heard something.