Flatseal won't start
bobo@bazzite:~$ flatpak run com.github.tchx84.Flatseal
(com.github.tchx84.Flatseal:2): Gtk-WARNING **: 16:55:40.263: Unknown key gtk-modules in /home/bobo/.var/app/com.github.tchx84.Flatseal/config/gtk-4.0/settings.ini
(com.github.tchx84.Flatseal:2): Adwaita-WARNING **: 16:55:40.353: Using GtkSettings:gtk-application-prefer-dark-theme with libadwaita is unsupported. Please use AdwStyleManager:color-scheme instead.
(com.github.tchx84.Flatseal:2): Gdk-WARNING **: 16:55:41.030: vkCreateSwapchainKHR(): Initialization of an object could not be completed for implementation-specific reasons. (VK_ERROR_INITIALIZATION_FAILED) (-3)
(com.github.tchx84.Flatseal:2): Gdk-WARNING **: 16:55:41.030: Could not create swapchain for this surface: Initialization of an object could not be completed for implementation-specific reasons. (VK_ERROR_INITIALIZATION_FAILED)
bobo@bazzite:~$ Solution
If countless command which didn't work, grok finally provided me one which starts Flatseal with XWayland, then Wayland actually works
flatpak run --socket=x11 --nosocket=wayland com.github.tchx84.Flatseal
