Hello,
the answer to your question depends on what you are using on your operating system and what packagers of your distribution suppose to be essential to LibreOffice. Taking a pure perspective of what is being delivered by TDF native rpm packages, you can just have a look into /opt/libreorffice<x.y>/share/fonts
to see which fonts are delivered with the software.
On the other hand, if you don’t know which package a specific font belongs to, just ask rpm database - See the following example for Waree font on Fedora:
[user@system:/usr/share/fonts/thai-scalable]$ rpm -qf /usr/share/fonts/thai-scalable/Waree.ttf
thai-scalable-waree-fonts-0.6.5-5.fc30.noarch
[user@system:/usr/share/fonts/thai-scalable]$ rpm -qi thai-scalable-waree-fonts-0.6.5-5.fc30.noarch
Name : thai-scalable-waree-fonts
Version : 0.6.5
Release : 5.fc30
Architecture: noarch
Install Date: Fr 02 Aug 2019 15:36:05 CEST
Group : Unspecified
Size : 394285
License : GPLv2+ and Bitstream Vera
Signature : RSA/SHA256, Mi 17 Jul 2019 10:03:09 CEST, Key ID ef3c111fcfc659b9
Source RPM : thai-scalable-fonts-0.6.5-5.fc30.src.rpm
Build Date : Mi 17 Jul 2019 09:43:10 CEST
Build Host : unused
Relocations : (not relocatable)
Packager : Fedora Project
Vendor : Fedora Project
URL : http://linux.thai.net/projects/thaifonts-scalable
Bug URL : https://bugz.fedoraproject.org/thai-scalable-fonts
Summary : Thai Waree fonts
Description :
fonts-tlwg provides a collection of free scalable Thai fonts.
This package provides the Waree family of Thai fonts.
This indicates that the font is not part of any LibreOffice package - but it may have been installed due packagers defined an dependency.
Finally - LibreOffice may ask the operating system (i.e. desktop managers), that additional fonts are required and a respective notification will be displayed, which allows to install the required additional fonts quickly. But nevertheless it is still not a font provided by LibreOffice but the operating system/ distribution.
Hope this helps