A big chunk of actual development of LibreOffice is done by a company called Collabora, that is also selling LibreOffice-based products for mobile and for cloud.
https://www.collaboraoffice.com
They seem to be the major contributor to LibreOffice Online (even still have their logo there?). Which is actually including the iOS and Android apps.
https://github.com/LibreOffice/online
On actual LibreOffice proper, which they call "LibreOffice Core", they seem to have 30% of commits, with RedHat also 30%.