Just for context Libdecor is a library that allows SDL2 applications (and possibly others in future) to draw CSDs on DEs that don’t implement xdg-decoration (GNOME). Libdecor should be able to use portals to query the cursor-size and cursor-theme if I’m understanding the code correctly:
https://gitlab.gnome.org/jadahl/libdecor/-/blob/master/src/cursor-settings.c#L75
When I check dbus-monitor and grep for cursor-size and cursor-theme, I can see the application does try to request the values. The cursor theme on my system is Yaru but it looks like DMZ-White is being used by the snap instead.
The flatpak of the same application with libdecor bundled gets the correct cursor on Fedora but curiously the flatpak on Ubuntu uses the default X11 style cursor. The snap consistently uses DMZ-White on both systems.
Unsure what’s going on, whether it’s a bug in libdecor or the snap sandbox is interfering.