xdg-open in distrobox fails because of missing display variables

[kaixiong]

Describe the bug

Using xdg-open to open links in browser (Firefox) fails:

$ xdg-open https://www.google.com
$ Error: no DISPLAY environment variable specified

xdg-open is symlinked to distrobox-host-exec:

$ ls -l $(which xdg-open)
lrwxrwxrwx. 1 root root 28 Dec 24 07:31 /usr/local/bin/xdg-open -> /usr/bin/distrobox-host-exec
$ /usr/bin/distrobox-host-exec xdg-open https://www.google.com
$ Error: no DISPLAY environment variable specified

The environment variables DISPLAY and WAYLAND_DISPLAY are not forwarded:

$ /usr/bin/distrobox-host-exec env | grep DISPLAY
$

FWIW, I'm opening links in an exported Emacs instance running under Ubuntu 24.04.

What did you expect to happen?

Link is opened in default web browser, no different from running xdg-open on host.

Output of bootc status

● Booted ostree
           Commit: 9841b7f08dcab66e744894fd023688f55fe2879460b8bb3f03d1bec34ec4c912

  Rollback ostree
           Commit: eb6a02ca257df9949340bdb74ba95c4ba2b1191fcb007f41b840d2e781aadfdd

Output of groups

**my-username** wheel video users render docker incus-admin libvirt steam

Extra information or context

No response