Emacs 28.1 does not provide any rendering support for the
Kharoṣṭhī (Kharoshthi) script. Such rendering support is needed
for the correct display of the script. Emacs 28.1 also does not
include an input method or a language environment definition for
the Kharoṣṭhī script.

Please find attached the necessary code for inclusion in Emacs 29.
The file “kharoshthi.el” is for the lisp/language folder, the file
“kharoshthi-input.el” (to be renamed to simple “kharoshthi.el”)
for the lisp/leim/quail folder.

I also attach a sample Kharoṣṭhī text and screenshots of this text
as rendered (incorrectly) in plain Emacs 28.1 and (correctly) in
Emacs 28.1 with my rendering code. The font used is Kharosthi
Unicode

   https://github.com/kharoshthiunicode/kharoshthi_unicode_font

which I separately activate in my init.el with the following:

   (set-fontset-font t 'kharoshthi "Kharosthi Unicode")

Maybe this font should be specified in the language environment
definition. If so, please add it.

(A font with even better support for Kharoṣṭhī is Segoe UI
Historic, but that font does not come with a free license. Noto
Sans Kharoshthi does not have adequate Kharoṣṭhī script support.)

For background information on how the Kharoṣṭhī script works, in
addition to the Unicode Standard please refer to the 2002 Proposal
to Encode Kharoṣṭhī in Plane 1 of ISO/IEC 10646:

   https://unicode.org/wg2/docs/n2524.pdf

I am one of the authors of this proposal and happy to answer any
questions not covered there.