Context: https://forum.k9mail.app/t/attachment-filenames-lost/6673/3
Opening an email PDF attachment and previewing it in Dropbox before I decide where I should upload it to is something I do very often.
However it seems that Dropbox isn't handling openable URIs correctly. It always uses the last segment of the URI, which is some sort of UUID, and always tells me that it cannot recognise files without extensions in their names. According to the linked post, Dropbox should probably use content resolver to get the the display name of the URI.