I did not need this before, because once we need to access the UI from remote, we already put an NGINX proxy in front (see this German post for a working NGINX config: UI am Raspberry konfigurieren - #2 by stefan.feilmeier)
According to…
…it might actually be sufficient to run UI via:
ng serve -c openems-edge-dev --host 0.0.0.0
Official docs is not very clear on that, unfortunately: Angular
Regards,
Stefan