Balena etcher is not even “loaded” but the key combination still tries to load the html email file.
I can’t see any “menu” options or docs to suggest why this key combination is doing this. Is it something in Balena etcher config?
I uninstalled Balena etcher and the behaviour has reverted to what is expected. The email is parsed into the default web browser.
Ideally I’d like to keep Balena Etcher available. So
NB Mu4e is being run in emacs 28.5 org-mode.