I'm using GNOME Wayland on Fedora 39 and I don't have the problem you describe. I just go to settings and select my keyboard layouts:

• English (US, intl., with dead keys)
• English (intl., with AltGr dead keys)

And everything just works. I specially like the second one because it doesn't interfere with keybindings in games, which can be a problem in GNOME Wayland.

Oh, I think I get the issue you're having, you can't find the Çç character on the Linux layout 😅 I always have to explain this to people migrating from Windows, it's AltGr+, (right Alt key plus Comma). I like this shortcut better than the Windows layout, but I understand some people might not like it. Unfortunately, I can't answer your question, as I too don't know how to customize the keyboard layout. I just got used to the Linux layout.

My situation is remarkably similar to yours down to the language, and I happen to have been considering a US keyboard as well so that's disheartening to hear. I have nothing to add right now but will let you know if I come across anything helpful!

I'm very happy to report that I found a solution to the problem: keyd. It's amazing.

• GitHub project here

• Credits for finding it

Instructions on the github project are crystal clear, but I'll leave some instructions below for Arch Users

yay -S keyd

sudo systemctl enable keyd && sudo systemctl start keyd

Now you can configure the /etc/keyd/default.conf file to your hearts desire. keyd is very feature rich, check the man page to see everything you can do. You can even add layers to your keyboard. Very sweet.

My personal configuration so far (I will definitely expand it later when I bump into more problems)

[ids]
*

[main]
' = oneshotm(apostrophe, ')

[apostrophe]
a = a
b = macro(space backspace apostrophe space b)
c = macro(backspace G-,)
d = macro(space backspace apostrophe space d)
e = e
f = macro(space backspace apostrophe space f)
g = macro(backspace apostrophe space g)
h = macro(space backspace apostrophe space h)
i = i
j = macro(space backspace apostrophe space j)
k = macro(backspace apostrophe space k)
l = macro(backspace apostrophe space l)
m = macro(backspace apostrophe space m)
n = macro(backspace apostrophe space n)
o = o
p = macro(space backspace apostrophe space p)
q = macro(space backspace apostrophe space q)
r = macro(backspace apostrophe space r)
s = macro(backspace apostrophe space s)
t = macro(backspace apostrophe space t)
u = u
v = macro(space backspace apostrophe space v)
w = macro(backspace apostrophe space w)
x = macro(space backspace apostrophe space x)
y = macro(backspace apostrophe space y)
z = macro(backspace apostrophe space z)

After editing /etc/keyd/default.conf make sure you run sudo keyd reload

Not an answer to you actual question, but: I stopped using dead keys long ago because I found it irritating to have to hit space whenever I needed to break out. Instead I mapped my CapsLock to be a Compose-key which lets me make almost any symbol I ever need in a very intuitive wsy. It works everywhere (incl. Wayland).