How does one configure the function called on an orgmode link such as file:~/Dropbox/ToProcess?

Question

I am using Org mode version 9.3 under GNU Emacs 27.1 (under Linux Debian). Typing enter on links such as file:~/Dropbox/ToProcess/ used to open the directory in dired-mode: I have a bunch of text automatisations based on this behavior.

At some point, emacs' behavior changed, nothing happening when selecting such link: It seems that it generates the message Running less /home/jbarbay/Dropbox/ToProcess/...done. I searched for an instance of less in my orgmode configuration file in particular and in all my emacs configuration files with no success. (Selecting links to specific sections in other orgmode files does work as intended.)

Typing enter on such links (correctly) calls the function 'org-open-at-point', which prints the same message when called directly. org-open-at-point 's documentation describes its behavior for such "syntactically correct links" relatively vaguely:

 On top of syntactically correct links, this function also tries
 to open links and time-stamps in comments, node properties, and
 keywords if point is on something looking like a timestamp or
 a link.

Does any knows what could have changed this behavior and how to return to the previous one, opening a folder into 'dired-mode'?

Answer 1

The variable org-file-apps controls which app is started on which file. Adding the following to one's configuration reset emacs to open a directory in 'dired-mode':

  (setq org-file-apps
               (append '(
                         (directory . emacs)
                         ) org-file-apps ))

Thanks to @NickD for the pointer to the variable org-file-apps !