Normally one defines all normal, bold, italic, bold italic font in alacritty. But since fira mono does not have italic font, how should the config structure look like?
Do you want another fonts italic style? Do you want Fira Mono on non-italic?
Then input that into the config.
Alacritty may have a fallback in place, if italic is left out, but I am not quite sure, since I use wezterm for its better display capabilities of font ligatures.
I use FiraCode Nerd Font Mono instead, but it also does not have a specific italic font. In my config, only the "normal" section is defined, but all my bold and/or italic text looks like it should. Apparently, alacritty will apply a heavier weight or slant to the "normal" type face if you simply omit the "bold" or "italic" sections. So, what you have right now should Just Work.
Allegedly, you can omit the "style" specification in the "italic" section (ie: just add "italic": {"family": "FiraMono Nerd Font"}, to your config snippit above), but i haven't actually tried doing it that way.
Yeah thats what I am going to use cuz before when I was using jetbrainsmono I had all the bold, bold_italic etc and suddenly just removing em all doesn't feel good to me.