

I choose to pay for remote access, but it’s for convenience and to support the developers. You are free to configure it yourself in a couple ways (and there is decent documentation) or do without remote access
I don’t know how you set up remote access for OpenHab, but from a quick glance at the web site it looks similar



I’ll also vote to reconsider WiFi. Home Assistant supports a variety of local mesh networks that by default can’t connect to the cloud and whose devices are cheaper and lower power.
I use all three of zwave, Zigbee, and thread; ha works with whatever you need.