Probably works better this way

backend/love.lua

@@ -14,6 +14,7 @@ local version = "0.0.1"
 
 -- Require stuff
 local uqt = require((...):match("^(.-ubiquitousse)%."))
+local m = uqt.module
 
 -- Version compatibility warning
 do
@@ -49,7 +50,7 @@ end
 uqt.backend = "love"
 
 -- uqt.event
-if uqt.event then
+if m.event then
 local updateDefault = uqt.event.update
 uqt.event.update = function() end
 function love.update(dt)
@@ -63,15 +64,17 @@ end
 local drawDefault = uqt.event.draw
 uqt.event.draw = function() end
 function love.draw()
-	love.graphics.push()
+	if m.draw then
+		love.graphics.push()
 
-	-- Resize type
-	local winW, winH = love.graphics.getWidth(), love.graphics.getHeight()
-	local gameW, gameH = uqt.draw.params.width, uqt.draw.params.height
-	if uqt.draw.params.resizeType == "auto" then
-		love.graphics.scale(winW/gameW, winH/gameH)
-	elseif uqt.draw.params.resizeType == "center" then
-		love.graphics.translate(math.floor(winW/2-gameW/2), math.floor(winH/2-gameH/2))
+		-- Resize type
+		local winW, winH = love.graphics.getWidth(), love.graphics.getHeight()
+		local gameW, gameH = uqt.draw.params.width, uqt.draw.params.height
+		if uqt.draw.params.resizeType == "auto" then
+			love.graphics.scale(winW/gameW, winH/gameH)
+		elseif uqt.draw.params.resizeType == "center" then
+			love.graphics.translate(math.floor(winW/2-gameW/2), math.floor(winH/2-gameH/2))
+		end
 	end
 
 	-- Stuff defined in ubiquitousse.lua
@@ -80,12 +83,14 @@ function love.draw()
 	-- Callback
 	uqt.event.draw()
 
-	love.graphics.pop()
+	if m.draw then
+		love.graphics.pop()
+	end
 end
 end
 
 -- uqt.draw
-if uqt.draw then
+if m.draw then
 local defaultFont = love.graphics.getFont()
 add(uqt.draw, {
 	init = function(params)
@@ -165,7 +170,7 @@ function love.resize(width, height)
 		uqt.draw.height = height
 	end
 end
-elseif uqt.input then -- fields required by uqt.input
+elseif m.input then -- fields required by uqt.input
 	uqt.draw = {
 		width = love.graphics.getWidth(),
 		height = love.graphics.getHeight()
@@ -173,7 +178,7 @@ elseif uqt.input then -- fields required by uqt.input
 end
 
 -- uqt.audio
-if uqt.audio then
+if m.audio then
 add(uqt.audio, {
 	-- TODO: cf audio.lua
 	load = function(filepath)
@@ -188,7 +193,7 @@ add(uqt.audio, {
 end
 
 -- uqt.time
-if uqt.time then
+if m.time then
 add(uqt.time, {
 	get = function()
 		return love.timer.getTime()
@@ -197,7 +202,7 @@ add(uqt.time, {
 end
 
 -- uqt.input
-if uqt.input then
+if m.input then
 local buttonsInUse = {}
 local axesInUse = {}
 function love.keypressed(key, scancode, isrepeat)

event.lua

@@ -1,5 +1,6 @@
 -- ubiquitousse.event
 local uqt = require((...):match("^(.-ubiquitousse)%."))
+local m = uqt.module
 local input = uqt.input
 local time = uqt.time
 local scene = uqt.scene
@@ -17,15 +18,15 @@ return {
 	-- @tparam number dt time since last call, in miliseconds
 	-- @impl mixed
 	update = function(dt)
-		if input then input.update(dt) end
-		if time then time.update(dt) end
-		if scene then scene.update(dt) end
+		if m.input then input.update(dt) end
+		if m.time then time.update(dt) end
+		if m.scene then scene.update(dt) end
 	end,
 
 	--- Called each time the game expect a new frame to be drawn.
 	-- The screen is expected to be cleared since last frame.
 	-- @impl backend
 	draw = function()
-		if scene then scene.draw() end
+		if m.scene then scene.draw() end
 	end
 }

init.lua

@@ -76,6 +76,17 @@ ubiquitousse = {
 	-- @impl ubiquitousse
 	version = "0.0.1",
 
+	--- Table of enabled modules.
+	-- @impl ubiquitousse
+	module = {
+		time = false,
+		draw = false,
+		audio = false,
+		input = false,
+		scene = false,
+		event = false
+	},
+
 	--- Backend name.
 	-- For consistency, only use lowercase letters [a-z] (no special char)
 	-- @impl backend
@@ -86,9 +97,12 @@ ubiquitousse = {
 package.loaded[p] = ubiquitousse
 
 -- Require external submodules
-for _, m in ipairs({"time", "draw", "audio", "input", "scene", "event"}) do
+for m in pairs(ubiquitousse.module) do
 	local s, t = pcall(require, p.."."..m)
-	if s then ubiquitousse[m] = t end
+	if s then
+		ubiquitousse[m] = t
+		ubiquitousse.module[m] = true
+	end
 end
 
 -- Backend engine autodetect and load

scene.lua

@@ -1,5 +1,6 @@
 -- ubiquitousse.scene
 local uqt = require((...):match("^(.-ubiquitousse)%."))
+local m = uqt.module
 local time = uqt.time
 
 --- Returns the file path of the given module name.
@@ -52,7 +53,7 @@ scene = {
 		return {
 			name = name or "unamed", -- The scene name.
 
-			time = time and time.new(), -- Scene-specific TimerRegistry, if uqt.time is enabled.
+			time = m.time and time.new(), -- Scene-specific TimerRegistry, if uqt.time is enabled.
 
 			enter = function(self, ...) end, -- Called when entering a scene.
 			exit = function(self) end, -- Called when exiting a scene, and not expecting to come back (scene may be unloaded).
@@ -116,7 +117,7 @@ scene = {
 	-- @impl ubiquitousse
 	update = function(dt, ...)
 		if scene.current then
-			if time then scene.current.time.update(dt) end
+			if m.time then scene.current.time.update(dt) end
 			scene.current:update(dt, ...)
 		end
 	end,