It might be pretty late, but you CAN change it in firefox (as well as in forks). I just put this in my user.js

user_pref("intl.date_time.pattern_override.connector_short", "{1} {0}");
user_pref("intl.date_time.pattern_override.date_short", "yyyy-MM-dd");
user_pref("intl.date_time.pattern_override.time_short", "HH:mm");

In gnome there’s dconf

But what if we gave each dinosaur an oxygen mask?

Insane Clown Posse would like to have a word with you

I use Fira Code, but any font patched with Nerd Fonts will do.

Personally, I like starship, and how it’s consistent across different shells. I mostly use defaults, but with line break before command.