When the fabric client uses RyoamicLights module, when bliss light and shadow are turned on, other players' hand-held light sources can't be seen, but BSL light sources can display normally.

I need to turn off the floodfill option to display other players' hand-held light sources properly.

this isn't a bug.
floodfill completely replaces the vanilla torch lightmaps. any mod that made use of those vanilla lightmaps or sort of injected into them, will not be able to function.