I am attaching the Org file and a screenshot of how it is rendered in Emacs and gEdit. 

Note that gEdit renders Grantha script with no extra action on my part. But Emacs won't render the Grantha script unless I explicitly set the font to be used. 


The Org file attached here is also availabe at https://github.com/casouri/valign/issues/27


In GNU Emacs 28.0.50 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo version 1.16.0)
 of 2021-07-08 built on debian
Repository revision: 7d6d14023a4ad7907c6e10ebdb49d78f9c6393e4
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)

Configured using:
 'configure -with-imagemagick --with-json --with-xwidgets'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
IMAGEMAGICK JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2
M17N_FLT MODULES NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS
TIFF TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM XWIDGETS GTK3 ZLIB

Important settings:
  value of $LANG: en_IN
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: iso-latin-1-unix