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.

In my 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.

But that setting has no effect. I can not get Devanagari characters to display in Eczar font.

How do I solve this problem?