Hello. This is my first post so I might be posting in the wrong place.
A few days ago I started having issues with perplexity and mammouth’s website. I couldn’t write accents. “é” ”è” or ”ê”. I found how to fix it but I thought it would be a good idea to report this issue. Just in case it could be an issue for a lot of other people.
My english isn’t really good so I asked a LLM to summarize this mess :

Description:

Since a recent system update (KDE Plasma 6.6+), it became impossible or unreliable to type accented characters (é, è, à, ù, etc.) using dead keys in web input fields when using firefox-pure on CachyOS with KDE Plasma under Wayland.

Environment:

• Distribution: CachyOS (rolling release, Arch-based)
• Package: firefox-pure
• Desktop environment: KDE Plasma 6.6+ on Wayland
• Browser: Firefox (as provided by firefox-pure)

Symptoms:

• Dead keys (e.g. ^ + e → ê) produce no accented character, or only the base character, in browser input fields
• The issue is specific to web input fields (e.g. perplexity.ai, mammouth.ai)
• The issue does not occur in native GTK applications
• The issue does not occur under XWayland (MOZ_ENABLE_WAYLAND=0 firefox)

Root cause:

The regression stems from a conflict between KDE Plasma’s default virtual keyboard (“Plasma Keyboard”) introduced or changed in Plasma 6.6 and Firefox’s input method handling under Wayland. The GTK_IM_MODULE environment variable is not set correctly for Firefox, causing dead key composition to fail in web content areas.

Workaround (confirmed working):

Launching Firefox with GTK_IM_MODULE=ibus resolves the issue immediately:

GTK_IM_MODULE=ibus firefox

Permanent fix:

Create a user-level .desktop override so the variable is always passed when launching Firefox from KDE:

mkdir -p ~/.local/share/applications
cp /usr/share/applications/firefox.desktop ~/.local/share/applications/
sed -i 's|^Exec=\(.*\)|Exec=env GTK_IM_MODULE=ibus \1|' ~/.local/share/applications/firefox.desktop
kbuildsycoca6 --noincremental

Alternatively, create a wrapper script at ~/.local/bin/firefox:

#!/bin/bash
export GTK_IM_MODULE=ibus
exec /usr/lib/firefox/firefox-bin "$@"

Suggested fix for the package:

It would be helpful if firefox-pure shipped its .desktop file with Exec=env GTK_IM_MODULE=ibus /usr/bin/firefox %u by default, or if a firefox-pure.sh wrapper in /usr/bin/ exported this variable before calling the real binary, so users on KDE Wayland are not affected out of the box.