In the meantime, if your have Alexa, she can now use custom commands in Routines so with the necessary virtual devices in HE, you could do a workaround. This would work for anything that works with Alexa but not HE yet.
In the end I managed to do this with Homebridge Running on a Raspberry Pi. The Gardena kit works well on Homekit, so it is touchable with a virtual device with a virtual Homebridge device and a Homekit automation behind that.
If you're doing it on an apple TV you still neeed something on the HE side to trigger the Homekit automation part. I'm using Homebridge and the HE app to push a button that triggers the Homekit App. If you've got an IFTTT account, you could probably use a virtual HE trigger for the Gardena skill using that instead of Apple.
I have a bunch of other Homekit automations, so Homebridge was a no-brainer for me. You need to be comfortable setting up a Linux environment and using command lines to do the installs on the Raspberry Pi, but otherwise not hard.