I might suggest Homebridge. That software, with a plugin, connects your Omni panel like its a Homekit accessary, then the Apple Home app. or other third-party Home apps. can control it perfectly.
So Homebridge is open source and runs on many platforms. Macs, PC, Raspberry Pi's etc. I run it on a Synology NAS. It just has to run 24/7. It is a bridge between your Omni panel and Homekit, which is Apple's home automation platform. Then I added the Alexa plugin. Now the Home app. on your iPhone can see all your units, zones, buttons, thermostats, etc. You can control anything, or set up automations as well. It is all free. I bought Home + which is an iPhone application for $15, and it lets you see and control your system much better than the Home app. but both work together. Oh, one final thing, you need either an iPad running at home, or an HomePod mini running. This is the server running Apple automations. The Apple HomePod mini is $99 and acts like an Alexa Echo but sounds better. So software is almost all free, but you need a processor to run Homebridge and a HomePod to run automations.
Other people have gone the Home Assistant route, with another Omni plugin, but personally, I wasn't impressed. Yes, its powerful software but a mess to manage, and you need a processor to run it on like Homebridge. If you use an iPhone, Homebridge is a better way to go, if you ask me. It will be up and running 10 times faster, and Apple handles all the access while you are outside your house. With Home Assistant, you have to do all that yourself.
Also, Homebridge and the Omni plugin are well maintained. The author of the Omni plugin just released an update yesterday. And Apple keeps updating the iPhone end of it.
Overall, the Homekit solution is far better than Haiku ever was. Home Assistant is fine if your a programmer geek type, but Homebridge is so much quicker to get running and so much easier to manage.
https://github.com/homebridge/homebridge
Also, with Homebridge Siri can control your home with your voice on your phone, watch, HomePod, and if you add the Alexa plugin, Alexa can control it as well.