Gnome Subtitles has a Wayland generic icon on KDE Plasma Wayland session
Gnome Subtitles 1.5 on Arch Linux.
Gnome Subtitles has a Wayland generic icon when running on KDE Plasma Wayland session. Maybe the following link can help you
https://community.kde.org/Guidelines_and_HOWTOs/Wayland_Porting_Notes#Application_Icon