Just follow these steps to backup WordPress Site to Dropbox with UpdraftPlus Free Version!
Step 1. UpdraftPlus Settings
Settings > UpdraftPlus Backups > Settings > Click on Dropbox Icon

Scroll down and click on Save Changes

Then, click on

Log in to Dropbox Account

Click on Complete Setup

and you will see

Step 2. Backup WordPress Site to Dropbox
Settings > UpdraftPlus Backups > Backup/Restore > Backup Now

Check on Send this backup to remote storage

In-Progress…

Done!

and Here is the Backup file

In Dropbox
