Long time user of OpenHab even though I just registered in the end of 2021.
My OpenHab journey already started with version 1.6.x and just a few items, such as 433Mhz devices.
Very soon my installation growed by a lot of Z-wave devices.
Meanwhile there were a lot of HUE devices, self manufactured sensors and irrigation control devices added to the installation.
Everything is build to minimize manual interaction needed to control any of these devices. Everything should run automatically and adopted to the habits of the people living in the house.
Most referred stuff on the server are the charts that I create with grafana.

Running multiple instances of OpenHab. Most stable one is the 2.5.12 release. Which is still in production.

Most recent system looks as follows:

ODROID C4 with 4GB of RAM
Ubuntu 20.04 headless
Running OpenHab 3.2.0 in a docker environment (docker-compose)
Alongside with

• influxdb
• mariadb
• grafana