If you're managing these Chromebooks through Google Admin Console, you can use Chrome Enterprise Policies to set and enforce certain settings. While there isn’t a direct "force allow audio" setting, you can try configuring the DefaultSoundSetting policy in a way that reduces issues with audio notifications.
In the Admin Console:
1. Go to Devices > Chrome > Settings.
2. Navigate to Content Settings.
3. Set DefaultSoundSetting to manage audio permissions (this will control how audio is played across sites, but might not guarantee full control over individual sites).
Unfortunately, forcing the audio setting for specific sites in MGS isn't natively supported, but policies like DefaultContentSettingValues could be explored.
2. Workaround - Persistent Profile Changes via Extensions:
You might be able to use Chrome extensions to force certain behaviors in guest sessions. For example, some Chrome extensions allow site-specific settings like sound permissions to be customized and persisted. You could deploy an extension that manages sound settings automatically.
3. Custom Script Deployment:
While not a built-in feature, you might consider a custom solution involving JavaScript or automation scripts. Some administrators use custom scripts to handle specific site behaviors on kiosk-mode devices. If your site allows it, a custom JavaScript that triggers notifications with audio could be embedded or linked.
Limitations:
Managed Guest Sessions are designed to reset after each session, meaning any changes you make are temporary unless explicitly configured via policy.
Chromebooks, especially in kiosk mode, have limitations on fine-grained site controls without administrative access.
To explore deeper options, you may want to reach out to Google support or explore the Chrome Developer Documentation for any updates on site-specific sound policy settings in MGS.