From the OH side of things, if one installs the Remote openHAB add-on (OH 3.0+) it should discover the HestiaPi and replicate and keep in sync all the Items that exist on the HestiaPi. The add-on can discover and work with OH 2.x even though the add-on wasn’t added to OH until OH 3. So from the OH side of things this is pretty much already done.
To support HA or other home automation software you will want to look at some sort of MQTT interface. Attempting to use the HA MQTT standard would make it discoverable by HA without manual configuration.