TL'DR

You can configure these settings from the Beeper Desktop by clicking on the Gear icon → Settings → Notifications → Advanced Settings

Notes

Differences between a notification that is “On” vs. “Noisy”:

A notification setting that is “On” will behave like a regular notification based on your device settings, but will not have an audible ring (and/or vibration) when you get notified

A noisy notification will have an audible ring and will override mute settings in case of mentions and display names. This is applicable even for chats that are marked as Low Priority. i.e. A message on a chat that is in Low priority (hence notifications are muted by default) will still receive an audible notification in case of a mention

Advanced Settings are Global i.e. you configure from Beeper Desktop but they will be applicable across all Beeper clients

On Beeper Desktop, in order for noisy notifications to work, please turn on the toggle “Enable audible notifications for this session” under Notifications (see screenshot above).