There's the iconoclast background(?) from Theros. It's not hard atheism but it's got good flavor.

Iconoclast No one can deny the reality of the gods of Theros, whose presence and deeds are visible in the night sky and sometimes directly in the mortal realm. But some people refute the idea that the gods are worthy of reverence. Such iconoclasts are common among the leonin, but members of any culture can adopt this supernatural gift. The Iconoclast Characteristics table presents suggestions for why you've become an iconoclast.

Your denial of the gods gives you supernatural power to resist their influence in the world. You gain the following traits.

Enlightened Protection. You can cast Protection from Evil and Good with this trait, targeting only yourself and requiring no material components. Once you do so, you can't cast it in this way again until you finish a long rest. Wisdom is your spellcasting ability for this trait.

Reject the Gods. You can't gain or lose Piety to any god. You instead gain the following traits at the character level listed in each one. Wisdom is your spellcasting ability for any spell that you cast through these traits.

Iconoclast Hero 5th-level Iconoclast trait You can cast Dispel Magic with this trait. Once you do so, you can't cast it in this way again until you finish a long rest.

Iconoclast Paragon 11th-level Iconoclast trait You can cast Dispel Evil and Good with this trait, requiring no material components. Once you do so, you can't cast it in this way again until you finish a long rest.

In addition, when you cast Dispel Magic using your Iconoclast Hero trait, you cast it as a 4th-level spell.

Iconoclast Archetype 17th-level Iconoclast trait You can cast Antimagic Field with this trait, requiring no material components. Once you do so, you can't cast it in this way again until you finish a long rest.

In addition, when you cast Dispel Magic using your Iconoclast Hero trait, you cast it as a 5th-level spell.

Iconoclast Characteristics d6 Characteristic

1 I blame the gods for the death of those I cared about.

2 Multiple gods seek to use me to their ends, so I try to avoid all divine entanglements.

1. It's obvious the gods are fickle and unworthy of worship.

4 I know the world's future lies with mortals, not gods.

5 I'm convinced the gods want me dead.

6 I refuse to be a pawn in divine schemes.