Since you asked what others with iOS are doing, I personally use HomeKit presence and then proxy it into smartthings with a device which can be seen by both platforms.
In the future, for those who have a SmartThings/Aeotec hub this will likely be an inexpensive matter smart plug, since those will run locally with smartthings, but for now I use a Meross power strip. That option does not require a ST hub.
(Also, we should note that any suggestion you find in the forums that requires an edge Driver will also require a smartthings/Aeotec hub since that’s where edge drivers run.)
Here’s a how-to write up I did on the method I use. It does not require an ST hub.
How to Use a Meross or Matter Plug to Use HomeKit Presence to Trigger ST Routines