What is the equivalent of emacsclient -a '' with emacs 27 on Ubuntu 18? I now get
$ emacsclient -a ''
emacsclient: file name or argument required
Try 'emacsclient --help' for more information
Without the fallback of starting an emacs daemon and then connecting again as had worked previously. This had worked on ubuntu 16.04 as well, so I assume it has something to do with Ubuntu 18.04.
You need to pass either -t or -n. If you want a GUI window: emacsclient -nc -a ''. If you want it to run in the terminal either emacsclient -t -a '' or emacsclient -nw -a '' will do what you want.