The problem stems from the fact that the home interface doesn't allow reading/writing to hidden folders in $HOME, and the ~/Private folder is actually backed by encrypted data in ~/.Private.
This is not specific to chromium, other strictly confined snaps using the home interface would be similarly affected.
Interestingly, saving a file to the folder still works, despite the error and the fact that the file dialog is unable to show the contents of the folder.
I can reliably reproduce the issue after creating an encrypted Private directory with ecryptfs- setup-private (see https:/ /help.ubuntu. com/community/ EncryptedPrivat eDirectory# Setup_Your_ Encrypted_ Private_ Directory).
The problem stems from the fact that the home interface doesn't allow reading/writing to hidden folders in $HOME, and the ~/Private folder is actually backed by encrypted data in ~/.Private.
This is not specific to chromium, other strictly confined snaps using the home interface would be similarly affected.
Interestingly, saving a file to the folder still works, despite the error and the fact that the file dialog is unable to show the contents of the folder.