I have the Gateway up and running from the pre built image (v8.1). Has anyone tried upgrading to v8.5 over and existing installed and running v8.1? Do I just copy the v8.5 files over the existing files in /home/pi/gateway and configure the settings in the Web app or are there other steps?
I would backup your working setup first.
Then you can try updating the changed files. Please see the releases github page (https://github.com/LowPowerLab/RaspberryPi-Gateway/releases) and there you can see the changes as well.
It will be a good idea to run npm update in the gateway dir to update the npm dependencies.
I would also look at the gateway category posts (https://lowpowerlab.com/category/iot-gateway/) for information and more details on changes.