TYPO3 Core

I can confirm the error. I have exactly the same problem with an 11.5.35. However, I have a second 11.5.35 TYPO3 where the problem does not occur. Unfortunately, I have not yet found the decisive difference between the two systems.

@Benjamin Robinson

can you confirm that the installation where the issue exists does not have 1:/user_upload mounted for editors, while the installation where the error does not happen does provides access to 1:/user_upload for editors?

Benjamin Franzke wrote in #note-4:

@Benjamin Robinson

can you confirm that the installation where the issue exists does not have 1:/user_upload mounted for editors, while the installation where the error does not happen does provides access to 1:/user_upload for editors?

No, in both installations editors don't have access to user_upload. But the installation with the issue has a user-TSconfig
options.defaultUploadFolder = 1:media/
The problem could have been that the editors don't have access to this default folder. This is now solved with the patch https://forge.typo3.org/projects/typo3cms-core/repository/1749/revisions/de0f48a7099fb320c50fd4635e11c1e4015690d9

@Benjamin Robinson

Thanks for the verification.
One last question to fully understand your case: I assume the editors do not have access to the configured folder 1:/media, right?

In that case the InsufficientFolderAccessPermissionsException would be triggered but not catched in https://github.com/TYPO3/typo3/blob/11.5/typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php#L1684-L1690 and thus no upload folder would be found (the alternatives that are resolved when the folder is missing are skipped in that case).
That explains how getSelectedFolder ended up returning false.

(Note: The fix you already verified is fine and sufficient and will soon be released, I just think we got a secondary issue here regarding correct behaviour here: inhomogeneous handling where defaultUploadFolder does not exist vs no permission)

Benjamin Franzke wrote in #note-6:

One last question to fully understand your case: I assume the editors do not have access to the configured folder 1:/media, right?

Yes, that's exactly how it is, the editors do not have access to the configured folder 1:/media

I didn't want the editors to upload files to user_upload in an unsorted and careless manner, but to put a little more effort into the directory structure. I overlooked the fact that they do not have access to 1:/media, but only to their own individual subdirectory.