SUMMARY

With the thunderbird's flatpak as the default mail client, share > send via email doesn't work. With  thunderbird or kmail installed as a native package, it work as intended.

STEPS TO REPRODUCE
1. Define the flatpak version of thunderbird as the default mail client
2. In dolphin, right click a file
3. CLick Share > Send via email

OBSERVED RESULT
qt.qpa.wayland: setGrabPopup called with a parent, QtWaylandClient::QWaylandXdgSurface(0x55ea4393e520) which does not match the current topmost grabbing popup, QtWaylandClient::QWaylandXdgSurface(0x55ea43f28100) According to the xdg-shell protocol, this is not allowed. The wayland QPA plugin is currently handling it by setting the parent to the topmost grabbing popup. Note, however, that this may cause positioning errors and popups closing unxpectedly because xdg-shell mandate that child popups close before parents
qt.qpa.wayland: setGrabPopup called with a parent, QtWaylandClient::QWaylandXdgSurface(0x55ea4393e520) which does not match the current topmost grabbing popup, QtWaylandClient::QWaylandXdgSurface(0x55ea43f28100) According to the xdg-shell protocol, this is not allowed. The wayland QPA plugin is currently handling it by setting the parent to the topmost grabbing popup. Note, however, that this may cause positioning errors and popups closing unxpectedly because xdg-shell mandate that child popups close before parents
qml: 
error: 'attachment='file:///home/kevin/Desktop/aezrzeareza'' is not a flatpak command. Did you mean 'document-unexport'?

See '/usr/bin/flatpak --help'

EXPECTED RESULT
Thunderbird windows open with the file attached to a new mail. 

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION