Set minimum light level to 1 for all nodes by adopting ambience_light mod - much more MC-like

mods/ENVIRONMENT/mcl_ambient_light/README.txt

@@ -0,0 +1,7 @@
+ambient_light by MikeRedwood
+============================
+Makes all nodes lit to a small degree!
+
+License of source code:
+-----------------------
+GNU LESSER GENERAL PUBLIC LICENSE Version 2.1, February 1999

mods/ENVIRONMENT/mcl_ambient_light/init.lua

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+local light_min = tonumber(minetest.settings:get("light_min")) or 1
+
+minetest.register_on_mods_loaded(function ()
+	for i, def in pairs(minetest.registered_nodes) do
+		local light_source = def.light_source
+		if light_source == nil or light_source < light_min then
+			minetest.override_item(i, { light_source = light_min })
+		end
+	end
+end)

mods/ENVIRONMENT/mcl_ambient_light/mod.conf

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+name = ambient_light
+description = Makes all nodes lit to a small degree!

settingtypes.txt

@@ -157,6 +157,13 @@ fix_doubleplants (Mcimport double plant fixes) bool true
 # Allow players to create Minecraft-like maps.
 enable_real_maps (Enable Real Maps) bool true
 
+# Minimum emissive light level below which the block is made to emit said light level. Defaults to 1 (looks like in MC).
+# WARNING! You may have to run fixlight on loaded areas after you remove it or change the light level.
+# Will work on all blocks including under ground.
+# For debugging mods or exploring underground worlds in creative mod author recommends 9.
+# Min 0 and Max 14.
+light_min (Minimum light level) int 1
+
 [Debugging]
 # If enabled, this will show the itemstring of an item in the description.
 mcl_item_id_debug (Item ID Debug) bool false