You should be able to integrate your IKEA and Homekit devices into the one if you use HomeAssistant.
The IKEA Tradfri system is all Zigbee based - I have a bunch of their light bulbs and strips, plus a few smart power plugs. I personally have them attached to my own Zigbee controller, but there's also a Home Assistant Tradfri integration if you want to keep using their Smart Hub controller.
There's also a Home Assistant homekit integration, so you can use HA to orchestrate events happening on the Tradfri side to trigger something in the Homekit side, or vice versa.
(I don't have the Tradfri smart hub or Homekit devices, so YMMV on specific possible options)
My beef is with the fact that the battery powered switch wants to be paired with the thing it directly controls and cannot be used alone with it just controlling something that is on the other side of the tradfri gateway. The five button round one apparently can be used for that, but the two position square one can't.
By the way the tradfri gateway is weird piece of hardware, the thing is mostly empty and only contains small board with apparently the same RFSoC as all the other tradfri peripherals connected somehow to ethernet PHY…
The IKEA Tradfri system is all Zigbee based - I have a bunch of their light bulbs and strips, plus a few smart power plugs. I personally have them attached to my own Zigbee controller, but there's also a Home Assistant Tradfri integration if you want to keep using their Smart Hub controller.
There's also a Home Assistant homekit integration, so you can use HA to orchestrate events happening on the Tradfri side to trigger something in the Homekit side, or vice versa.
(I don't have the Tradfri smart hub or Homekit devices, so YMMV on specific possible options)