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Can a Divine Soul Sorcerer learn a cleric cantrip at the first sorcerer's level? Or just at higher level?

Divine Magic

Your link to the divine allows you to learn spells normally associated with the Cleric class. When your Spellcasting feature lets you learn a sorcerer cantrip or a sorcerer spell of 1st level or higher, you can choose the new spell from the cleric spell list or the sorcerer spell list. You must otherwise obey all the restrictions for selecting the spell, and it becomes a sorcerer spell for you.

and

Sorcerer Spellcasting

You know two 1st-level spells of your choice from the sorcerer spell list.

A literal reading of the Spellcasting Feature says that you know your starting spells, not that you learn them. However, the wording of Divine Magic, which you get at level 1, also goes on to say:

In addition, choose an affinity for the source of your divine power: good, evil, law, chaos, or neutrality. You learn an additional spell based on that affinity, as shown below. It is a sorcerer spell for you.

So regardless of how you interpret the know/learn wording of the spellcasting feature, the latter part of Divine Magic absolutely says that you learn a spell at the first level and therefore may choose to learn a Cleric cantrip instead.