I'm using the Files app on my iPhone and iPad to save photos to an SMB network share provided by Samba on an Ubuntu 20.04 server.
Since around iOS/iPadOS 14.5, trying to save a new file to the share results in an error message saying:
The operation couldn't be completed Operation canceled
Since nothing has changed server-side, this looks like a bug in iOS/iPadOS. How can the described problem be solved?