I'm able to normaly use dead keys over the whole system.
FYI I live in Brazil and we use accented letters, as in é á ó ã õ.
We need dead key support for this as we type first the accent key " ´ " and then the proper key " a " to get and á
It doesn't work in terminals like 'st' and 'urxvt' tough. I've searched thoroughly over the internet to no avail.
EDIT:
Change keyboard layout (English UK) on command line to English US doesn't solve my problem, as it is urxvt and st related.
Modern terminals like "tilix" or "gnome-terminal" are able to produce "á é é" characters
I have the English US keyboard, and I switch to the English US International keyboard with dead keys to type accents in Spanish. I have no issue typing accents in urxvt. I am using Debian 11.
To set my keyboard, I can use the commands:
Furthermore, I have a keybinding set to run this script to toggle between keyboard layouts: