I had faced the similar problem earlier and found a solution myself here. But I am stumped now.
I am running Doom Emacs 3.0.0 on Emacs 27.2 on Gnome 40.4.
config.el, there is:
(set-fontset-font t 'devanagari "Eczar")
I have installed Eczar font.
font-counsel shows Eczar as an option.
set-frame-font shows multiple Eczar entries --- I guess, one each for a variant. I can select any of these and the change is reflected immediately. I can do Options -> Set Main Font and select Eczar. And like in the previous case, the change is reflected immediately.
But that setting in
config.el has no effect. I can not get only Devanagari characters to display in Eczar (or any other) font.
describe-char shows the font Gotu. I had used that earlier.
How do I solve this problem?