When I updating Libreoffice, installer removes all noto sans fonts (maybe also also another fonts).
Workaround: completely remove previous version and install new version from scratch. Then Noto Sans fonts are present in the system.
For example, I have LO 6.0.2 installed on my system. Then I want update it to 6.0.3. Then I run installer and picking custom installation. Installer updating LO from 6.0.2 to 6.0.3 but Noto Sans fonts becomes unavailable in all documents which use this font.
If I completely uninstall old version and install new version - then fonts are present as expected.
Fully fixed for 6.1.0 and master, with functional patch at 6.0.4 builds.
*** This bug has been marked as a duplicate of bug 116581 ***