Note: when scholars mention Islam as a condition for the obligation of Salaah, Zakah, Sawm, etc., what's intended is that these acts of worship are not accepted

الكفار مخاطبون بالفروع (1) The Āyat from Sūrah Al-Muddathir clearly prove that they will be punished for this. So, when a Muslim feeds them, he is actually aiding them upon sin and transgression, which is in direct opposition to Allah's command: {وَلَا تَعَاوَنُوا۟ عَلَى ٱلۡإِثۡمِ وَٱلۡعُدۡوَ ٰ⁠نِ} “Do not help one another in sin and transgression.” [Surah Al-Mâ'idah: 2] He is sinful for aiding them, and they are sinful for disbelieving in Allāh and disobeying His commandments. Footnote: (1) Sheikh ‘Uthaymīn raḥimahullāh said: “The same is required from a kāfir as is required from a believer (in terms of religious duties), but he (the Kāfir) is not obligated with that in this world...” [Majmū’ Fatāwa Sheikh Ibn ‘Uthaymīn (2/question no. 164)] ____ Sheikh ibn Bāz rahimahullah mentioned that it's not permissible for Muslims to feed the Kuffār during Ramaḍhān. https://binbaz.org.sa/fatwas/4195/%D8%AD%D9%83%D9%85-%D8%AA%D9%82%D8%AF%D9%8A%D9%85-%D8%A7%D9%84%D8%B7%D8%B9%D8%A7%D9%85-%D9%84%D9%84%D8%B9%D9%85%D8%A7%D9%84-%D8%BA%D9%8A%D8%B1-%D8%A7%D9%84%D9%85%D8%B3%D9%84%D9%85%D9%8A%D9%86-%D9%81%D9%8A-%D9%86%D9%87%D8%A7%D8%B1-%D8%B1%D9%85%D8%B6%D8%A7%D9%86 The above applies in the case where one is sure that this person is not excused from fasting Ramaḍhān. As for giving food to children, the sick, travellers, or anyone else who has a legitimate excuse, then this is permissible.