I am using Wayland Plasma session, first without defining a keyboard layout, because I assumed the layout would be copied from the chosen layout during installation. That layout is: US with dead keys (US int.). However I could not enter an accent using the that key followed by pressing the space bar. Instead the popup appears to enter a command like when using <Alt>+<f2>. It is the same for other dead key characters. After that I started systemsettings5 and found that no keyboard layout was active, so I configured US+int. (US with dead keys). I had the impression - can't remember for sure - i could enter character using dead keys. However after a reboot and starting a Wayland Plasma session again, the wrong behavior was back. Using systemsettings5 to inspect the layout of the keyboard, the configuration with US with dead keys was still there. Adding a normal US keyboard and getting the ability to switch between these layouts, I found that US with dead keys did not what I expected. In the test I used konsole to enter text.
Cannot reproduce, after reboot dead keys are entering normally in Konsole. I use Right Alt key as a modifier for dead keys input though Plasma: 5.13.1 Apps: 18.04.2 Frameworks: 5.47.0 Qt: 5.11.1 Kernel: 4.18.0-1-MANJARO OS: Netrunner Rolling Video: Intel 4400 Driver: xf86-video-intel 1:2.99.917+831+ge7bfc906-1 Mesa 3D: 18.1.2 Screen: 1600x900 Xorg: 1.20 Wayland: 1.15.0-1 Wayland Protocols: 1.14-1
Tried again with the newest version of openSUSE Tumbleweed and found the same issue. Keyboard setting is US int. with dead keys. But when I press key ' followed by a space, character ' does not appear, simply a space. It is the same when I press key ' followed by key e, character é should appear, however a simple e appears.
I can confirm that this is a real issue, and it is related to Wayland. Every app works normally on Plasma/X11. However, the problem seems to be limited to Plasma apps, like Konsole, Dolphin and KCharSelect. Dead keys are working in Firefox (which on my machine is a Wayland app), Chromium (XWayland), Emacs (XWayland), etc. I am not using a compose key. I have a Finnish keyboard; my only keyboard configuration is /etc/vconsole.conf which contains the setting KEYMAP=fi
*** Bug 427793 has been marked as a duplicate of this bug. ***
This sounds like the same issue as #411729 which was posted later but has more information.
I am also affected by this. Arch Linux, KDE, Wayland, Brazilian keyboard.
I'm affected by this too, with a UK-extended layout. The accent mark is not working. The issue seems to only be present in Qt applications.
*** This bug has been marked as a duplicate of bug 426621 ***
*** This bug has been marked as a duplicate of bug 411729 ***