Not obvious how to use `emacsclient` from host

In other environments, I would normally fire up Emacs and then interact with it calling `emacsclient` directly from the command line (e.g., `emacsclient /some/path/some/file`). However it is not obvious how to do this when Emacs is running via `flatpak`. It would be nice if this was documented.

After reading https://www.reddit.com/r/flatpak/comments/w4aoih/launch_application_emacsclient_from_within_a/, I came up with something like `flatpak enter org.gnu.emacs flatpak-spawn --host emacsclient …`, but that seems somewhat absurd and results in the following error:

``` sh
% flatpak enter org.gnu.emacs flatpak-spawn --host emacsclient /some/path/some/file
emacsclient: can't find socket; have you started the server?
emacsclient: To start the server in Emacs, type "M-x server-start".
emacsclient: No socket or alternate editor. Please use:

--socket-name
--server-file (or environment variable EMACS_SERVER_FILE)
--alternate-editor (or environment variable ALTERNATE_EDITOR)
```