I need to replace a large old-style Frigidaire AC unit that's built into a wall with a Ductless unit, something like a Mr. Cool. Can someone advise brands that will work with HA via WiFi, Zwave, or inter-operate with an Ecobee T-stat?
ETA: Heat is not necessary, but if there's a model that works with HA and it's both, so be it.
You are asking a very broad question, that most vendors have solutions for.
Identify your HVAC requirements first, find units that match these, and then see if they have HomeAssistant support.
Your friendly local HVAC Installer will probably be a good source of advice, knowing far more about reliability and ease of use than a salesperson intent on getting maximum profits from you.