In Skype on Ubuntu, you can click a little folder icon next to a download to open the directory containing the download:
When I click the folder icon, the folder is always opened in Nautilus? How do I change the file manager used to open this file?
Skype uses a program called mimeopen
to open the folder.
To choose a new default file manager to open directories, run this in a terminal:
mimeopen --ask-default ~/Downloads/
You should get output similar to the following:
Please choose a default application for files of type inode/directory
1) Files (nautilus)
2) Disk Usage Analyzer (baobab)
3) Files (nautilus-folder-handler)
4) Open Folder with Thunar (Thunar-folder-handler)
5) Other...
Simply choose the correct number, and Skype should use your default choice from now on.