You've hit the nail on the head. The solution is for the OP to wait until closer to the contracted performance date and then see whether the service can be completed. If it can, swallow the loss. If it can't, negotiate for a partial or full refund due to inability to perform.Warning! Unpopular opinion
But the wedding was scheduled in October, not June. That's 6 months away. What does the contract say? If COVID were taken out of the equation, no one would be suggesting that the deposit should be returned, especially if the contract stipulated that the refund is non-refundable.
At the end of the day, I do not feel that the venue or photographer have a moral obligation to refund the deposit, unless they are unable to provide the goods and services. If the wedding were next week, then that's a different scenario, but 6 months later?