Control4 -> Hubitat

would most definitely mention to your agent. In the US at least, if a house is shown with something hard wired, plumbed, etc and it isn't stipulated that it would be removed by the seller in the agreement, it's a breach of agreement. What Property Can I Remove From Home I'm Selling | Lawyers.com

The C4 system is no more or less a fixture than any non smart system. Is there some gray? Possibly. But there's nothing egregious in the OP's case that I see.

The OP has:

  1. a controller, which is the brains of the system. It's functionally similar to a Hubitat hub with additional AV capabilities.
  2. dimmers & locks. The only things that are clearly fixtures. They will work without the controller, similar to smart switches in a Hubitat home that not connected to a controller. The only lighting controls that don't work without the controller are keypads, but there's no note of them in this thread.
  3. an audio amplifier. Unclear whether there is a switch there or not.
  4. remote controls

The things that may be missing from the system: an audio receiver/amp for the outdoor zone, and maybe a matrix audio switch. That's it. I don't know of anyone who would think audio receivers and amps are definitely fixtures. Built in speakers would be fixtures, but there's been no mention of any speaker issues.

Even if those components were still in the house the OP would still need to get a dealer involved. The network equipment, TVs, soundbars, cable boxes, streaming devices, any audio streaming services, all need to be added and/or configured. My dealer charged $350 to do all that. Which seemed fair.

When I bought my house it was clear there was a control system and I made sure that it was listed in the contract. In my case a system is necessary due to centralized rack mounted AV components. Would it have been considered a fixture? Gray, again.

I have both in my house and have purchased the chowmain tcp driver for C4. Using it with Maker API you can integrate between the 2 systems. I had ifttt driver before but tcp is much better since it is all local

AV equipment, if it was integrated at the time of showing, must remain in the house after sale, unless agreed upon before the sale.