Collabora Online uses Collabora Office as its backend, which comes with a large variety of free fonts, see the list below:
Carlito, which are metric-compatible with
Google Open Sansand
Google Noto(full Unicode coverage)
Liberation Serif, which are metric-compatible with
Times New Roman
Linux Libertine G
Source Code Proand
Source Sans Pro
When you install coolwsd package, the post-install script will look for additional fonts on your system, and install them for Collabora Online (in the systemplate). If you install fonts to your system after installing coolwsd, you need to update the systemplate manually and restart coolwsd service.
In Collabora Online 22.05.7 the possibility of remote font downloading was introduced. This method does not require restart of the coolwsd service, remote fonts become available for new editing sessions within a minute. See the details in Remote configuration chapter.