How do I restore an earlier data set from Dropbox?
Information from a note was inadvertently deleted and I want to restore it from an earlier backup.
How do I do this? Your support notes appear to mention every other option than Dropbox despite this being one of your prompted sync targets.
If you have been making backups using the Joplin backup plug-in a method to extract a single note from a JEX export/backup file can be found here on the backup plug-in README.
Dropbox is a sync target used to get data from client to client it has never been a form of backup. I am not a user of Dropbox but can you search Dropbox for any file (including any in trash) that contains some of the text you are looking for? If it is still there (i.e. not been flushed yet) you could then just copy the text and paste it into a new note. Of course if you have End-To-End Encryption (E2EE) switched on this will not be possible as all the notes on Dropbox will be encrypted.