I have done some more thinking and testing. I tried to upload the app log to a folder on Nextcloud via the iOS Files app and got the error message “File or folder does not exist”. But in fact the log file was uploaded to the selected directory (checked in Nextcloud App). This is very strange. Of course, I can’t view it in any app (except the Nextcloud App itself). I guess browsing the directory tree from level 1 doesn’t work.