What is the ruling on one who masturbates intentionally during the daytime in Ramadan and is unable to fast?

Congratulations on your repentance. We ask Allah to accept it and reward you for your steadfastness. Regarding masturbation during the daytime in Ramadan, only making up the day (qada') is required, according to the more preponderant opinion. If your inability to fast is due to an excuse that is expected to be temporary, then make up the fast after the excuse is gone. However, if the excuse is not expected to be temporary, such as a chronic illness, then expiation (kaffarah) is required, which is feeding one poor person.