Why is it so complex and difficult to install and maintain HomeAssistant?

FWIW, if you wish, you could continue to use Hubitat Elevation as a Zigbee/Zwave hub and have it communicate with Home Assistant via a custom Hubitat integration.

Alternately, you can recoup some of your investment by selling it. I’m not sure if and how you can transfer Homeseer’s license but I believe you can for Hubitat.