At some point it was in the statusbar, but there is no statusbar anymore. At some other points it was next to each message, but that was noisy, slow and was removed. So now you send messages, they may fail and internally it is known, but it isn't displayed. A new error disclosure message is definitely needed. Maybe also playing with the color or opacity of the outgoing messages.
Kirigami's PassiveNotification may be of use here.
This project is unfortunately no longer maintained. If a new maintainer wants to step up and take care, the project is archived here: https://invent.kde.org/network/ring-kde You can just clone it in your private namespace on invent.kde.org and if you have started to work on it and fixed/implemented something get it reviewed and the project unarchived. Sorry for the inconveniences.