Hey there,

You can add the following custom CSS code into Backend > EasyDiscuss > Settings > Custom CSS and you need to adjust the font size according to your liking:

body #ed {

    font-family: Montserrat;

}



:root {

    --si-root-font-size: 1.8rem;

    --si-font-size--01: 1.35rem; 

    --si-font-size--02: 1.6rem; 

    --si-font-size--03: 1.65rem;

    --si-font-size--04: 1.75rem;

}

For your information, all the 5 sizes are related and in-used in EasyDiscuss.

You will need to inspect the HTML element and see which CSS variable is used in the element.
E.g. https://take.ms/p5Yy7

In the above case, the H2 element is using --si-font-size-003 which equivalent to font-size 17px.
17px * 1rem and the 17px is from your current template global font-size. Please see: https://take.ms/rVELi

Can you give it a try and see how it goes?

Do clear all of your caches before you see the changes.