Dear Maintainer,

According to the Hexchat FAQ
[https://hexchat.readthedocs.io/en/latest/faq.html#how-do-i-change-what-browser-is-opened]
in order to configure the file association for http and https links the
user is directed to use the 'gio' utility.  For example:
  gio mime x-scheme-handler/http firefox.desktop
  gio mime x-scheme-handler/https firefox.desktop

For users of KDE these commands will not run successfully, and other
methods of configuring http and https mimetype associations such as
setting [Default Applications] in ~/.config/mimetypes.list or in
~/.local/share/applications/mimetypes.list also have no effect.

Also note that the other two examples in the fact which use gvfs-mime
will not work either in Bullseye because gvfs-mime is deprecated and
points to gio.

The end result is that it is not possible to configure the http and
https mime type associations for Hexchat.

Instead, Hexchat should use a destkop-environment-neutral mime mechanism such as
xdg-mime.

Found the source of the issue with the gio command when running:

$ desktop-file-install --dir=$HOME/.local/share/applications
.local/share/applications/firefox.desktop

value "\\$HOME/.local/firefox/firefox %u" for key "Exec" in group
"Desktop Entry" contains a reserved character '$' outside of a quote

Adding quotes didn't help.  The solution was to hard-code my home
directory in the Exec= line instead of using $HOME.  Then the gio
command successfully runs:

$ gio mime x-scheme-handler/http firefox.desktop
Set firefox.desktop as the default for x-scheme-handler/http

$ gio mime x-scheme-handler/https firefox.desktop
Set firefox.desktop as the default for x-scheme-handler/https

$ gio mime x-scheme-handler/https
Default application for “x-scheme-handler/https”: firefox.desktop
Registered applications:
         firefox.desktop
         chromium.desktop
         kfmclient_html.desktop
Recommended applications:
         firefox.desktop
         chromium.desktop
         kfmclient_html.desktop

Dear submitter,

as the package hexchat has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1120756

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)