I picked up a nice IR sauna on Craigslist a couple of years ago and am in the process of moving it outside next to the hot tub. The digital control panel's UI is cumbersome to use and this appliance seems ripe for conversion.
Seems like something that would be a rather large effort.
I wanted to do this the day we purchased ours, but my wife talked me out of it for warranty protection purposes. Now that that time has passed, I'd like to do it but am short on time. I don't know that it would be all that hard, though. Seems like some soldering to mimic the push buttons might accomplish what's required, but one would want to test it thoroughly to understand the circuits, of course, before diving in. I just haven't done it. If you do so, would be interesting to follow. I find having to traipse down and turn the thing on, then wait for it to get warmed up, rather annoying. These things are not well designed, in my view, for a great user experience.
if you're just simulating button presses, you can use a relay to achieve this. i'm simulating a button press with my garage door and the garage door opener. i hooked up the relay in parallel with the button, so the button still works, but i can trigger my relay and it also activates the button
There are IR transmitters that work with Rule Machine and such. I have an IR 'puck' that I paid $11 for when on sale. I re-flashed it with Tasmota, and added it to HE. The device can learn IR codes when a remote is pointing at it. Those learned coded can then be custom attributes in Rule Machine, Event Engine, etc..
It sounds complex, but if you have the remote for the device, you could create automations that will basically press the buttons of a physical remote.
I created rule machine rules for mine doing a simple power off the TV and power off the Onkyo at 2am every day, in case it was left on... Do you have the remote for it?