Cause: Older versions of the HarfBuzz shaping engine or a corrupt font cache. Solution:

Same as above—download the valid AptSangam.ttf file.

For the uninitiated, the search query itself reveals a common pattern: users trying to translate a Windows or GUI-based logic to the Linux terminal. The correct syntax does not exactly match the keyword; instead, the correct command is:

sudo apt install fonts-sangam-tamil

Let's deconstruct why users search for apt sangam tamil fonts install and how to correct it:

The exact package name is crucial. Running apt install sangam tamil will fail because APT looks for two separate, non-existent packages.