I got an Xception model.
Xception = tf.keras.applications.Xception(input_shape=(512, 512, 3), include_top=False)
I have combined the model to change the Input Channel to 3.
input_layer = keras.Input(shape=(512, 512, 1), name="img_input")
x = layers.UpSampling3D(size=(1, 1, 3), name="output")(input_layer)
input_model = keras.Model(input_layer, x, name="input_model")
model = keras.Model(input_model, Xception, name="model")
however I have got error
Input tensors to a Functional must come from `tf.keras.Input`. Received: <tensorflow.python.keras.engine.functional.Functional object at 0x7f922942a690> (missing previous layer metadata).