I did tried in my focal VM with both xdg-utils and claws-mail and it worked here (see attached image). In claws it opened a gtk stuff, with settings steps and a window with the message to be composed and the attached file.
Maybe someone else in this bug/thread has any idea what is happening.
As the security update was already reverted I don't see any ways it can be security related with the sec update.
I did tried in my focal VM with both xdg-utils and claws-mail and it worked here (see attached image). In claws it opened a gtk stuff, with settings steps and a window with the message to be composed and the attached file.
Maybe someone else in this bug/thread has any idea what is happening.
As the security update was already reverted I don't see any ways it can be security related with the sec update.