Setup

aur sync -c onlyoffice-documentserver
pacman -Sy onlyoffice-documentserver postgresql rabbitmq redis caddy
systemctl daemon-reload
systemctl start postgresql rabbitmq redis
sudo -i -u postgres psql -c "CREATE DATABASE onlyoffice;"
sudo -i -u postgres psql -c "CREATE USER onlyoffice WITH password 'onlyoffice';"
sudo -i -u postgres psql -c "GRANT ALL privileges ON DATABASE onlyoffice TO onlyoffice;"
psql -hmysql.pi -Uonlyoffice -d onlyoffice -f /usr/share/webapps/onlyoffice/documentserver/server/schema/postgresql/createdb.sql
systemctl start onlyoffice-docservice onlyoffice-fileconverter onlyoffice-spellchecker

Create web server config file at /etc/caddy/caddy.conf.d/officepad.de.conf:

officepad.de:80 {

	root   /home/onny/projects/onlyofficepad
	log    /var/log/caddy/officepad.de_access.log
	errors /var/log/caddy/officepad.de_errors.log

    proxy /spellchecker http://localhost:8080 {
        transparent
        without /spellchecker
    }

    rewrite {
        r ^/(cache|downloadas|sdkjs|plugins.json|fonts|web-apps|upload|doc)
        to /proxy/{uri}
    }

    proxy /proxy/ http://localhost:8000 {
        websocket
        transparent
        without /proxy/
    }

    proxy / http://localhost:8082 {
        transparent
    }
}

Append to /etc/hosts:

[...]
127.0.0.1	officepad.de

systemctl restart caddy
git clone https://git.project-insanity.org/onny/onlyofficepad.git
cd onlyofficepad
env NODE_ENV=default node bin/www

Visit http://officepad.de in your browser :)

Change default port of onlyofficepad in config/default.json.