With macOS Catalina and later, the local Library StickiesDatabase file which is a digest of individual stickies has not been used by the Stickies application.
As part of the operating system upgrade, each digest entry (stickie) in that file has been extracted and written into a serialized RTFD package, each containing the original stickie digest entry as TXT.rtf. The Stickies application in Catalina and beyond is now aware of these RTFD packages and it is they that it presents when launched.
The individual digests from the original StickiesDatabase file now reside in this location, where they are not intended for user interaction:
/Users/username/Library/Containers/Stickies/Data/Library/Stickies/