Hi Tobias,
I noticed this in today's Release Notes:
Web-based phone volume settings
PureCloud web-based phone users can now adjust call ring and audio volumes separately. For more information, see Select the PureCloud web-based phone as your phone.
https://help.mypurecloud.com/articles/select-purecloud-web-based-phone-as-your-phone/
Are you seeing those separate Ring and Call volume controls now?