Only Office Configuration

Hello, I’m using OnlyOffice with Nextcloud Hub 8/9, but I’m having trouble configuring it correctly. I’ve tried various options in the config files but still can’t get it to work. I also have a few questions:

  1. Is OnlyOffice free, or do I need a subscription now?
  2. For the secret key, is it the one specified in the config.php file of Nextcloud?
  3. Which server address should I enter? My Nextcloud URL is https://1234/nextcloud. What exactly should I put in the “OnlyOffice document server” field? Should I use the OnlyOffice server URL from OnlyOffice, or is it my own server URL (e.g., https://1234/nextcloud/??????????????????)?

Thanks for the help!