I can add a few more observations to this post.
I built and installed the above snap on a 20.04 desktop system.
git clone https://github.com/ogra1/electron-kiosk-wayland.git
cd electron-kiosk-wayland/
snapcraft
snap install --dangerous *.snap
snap connect electron-kiosk-wayland:wayland
On Mutter
Forcing the snap to run on GNOME/Wayland I see the “everything painted white” issue around 3/4 runs. But the mouse scroll works.
snap run electron-kiosk-wayland
On Mir
I also tried running on Ubuntu Frame:
snap install ubuntu-frame
export WAYLAND_DISPLAY=wayland-99
ubuntu-frame&
snap run electron-kiosk-wayland
Again, this paints everything white around 3/4 runs. But, as you’ve observed on RPi4, the mouse scroll doesn’t work.
As a sanity check, I tried running both gedit and kate on Ubuntu Frame (by starting them from the same terminal session) and both were working with the mouse scroll wheel.
gedit snap/snapcraft.yaml
QT_QPA_PLATFORM=wayland kate snap/snapcraft.yaml
Conclusion
It would seem probable that both the “everything painted white” and the mouse scrolling issues are failures in electron’s current level of support for Wayland (i.e. not with snaps or Ubuntu Frame).
I will have a closer look at any differences in the mouse axis handling between Mutter and Mir, but as both GTK and Qt are working correctly it is likely electron is doing something unusual.