I’ve not tried SmartThings. I was planning to import one until I saw all the issues people were having. That, combined with the fact that I don’t want to have to rely on a cloud and Samsung’s commitment to a system to run my house.
I already have a homeserver and after some research it turned out Domoticz works with a simple package, but if it didn’t you can have it run from a Raspberry Pi too. All very cheap, all open source and reasonably simple to setup. And so far it has proven to be reliable and it all works locally. Don’t know if it’s a viable option for you as it’s more work than SmartThings claims their platform is and so far I’m not running more than 10 devices, but you could have a look at it.