@attis Thanks for debugging, I added a new config setting into config.json, you can set isCluster: true in your config.json and it should work now. It will be available in 1.9.2 so you can keep your change until then. https://github.com/NodeBB/NodeBB/issues/6509
I fixed my own issue. Apparently some install scripts fail when run as root (or with sudo). I'm not sure why this is the case, but I got everything to work by running sudo chown -R ralph:www-data /path/to/nodebb && ./nodebb upgrade as a standard user.