The flange is about 7" OD. As you can see both slots where the closet bolts would go are broken. Can I salvage this flange somehow, instead of having to rip it out of the concrete and installing a new one?
They make toilet flange repair rings. I don't have any personal experience, so I can't say how durable they are, but for a couple bucks it's worth a try. You can see that there are holes to screw through the plastic flange holes, so in your case I'd get a good concrete bit and some tapcon screws.
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I think it's toast. Even if you could salvage it, you'd probably regret it later when the toilet starts rocking and leaking.
Do it right, replace it.
You just need to remove a small amount of concrete around it, shouldn't be much work with a chisel.