I have not been in this position but I do know of someone that has.
I dont know all the details but the bio Dad was happy to give up all rights to the children because that meant he didnt have to pay child support and he could move on with his life. He happily signed all papers and everyone was happy.

I wish you luck in this, I looked into my hubby adopting my son, who we both say is our son, and our son calls him Dad, and knows that he has another father out there who has had zero effort in his life.
When I looked into adoption, it was going to be a costly and lengthy process that involved psychological assessment of the child to ensure they knew what was happening and even after the costs and process, there was no guarantee that the adoption would be allowed.
Seek legal advice from a lawyer, they will be able to advise the whole process to you along with costs.
My biggest wish is that we could just say this is my child’s father, the man who is raising him and loves him as his own.

How sad for your daughter that her biological dad doesn’t make contact. I wish you all the best in making her chosen dad her legal dad

I don’t know the answers and I urge you to get proper legal advice.

My step-dad adopted me just after marrying my Mum. Laws have probably changed now but I was already calling him my Dad anyway. Maybe get in touch with someone in the legal department and ask them what they can suggest. Wish you all a most wonderful life together.

The are formal requirements for adopting a step child.
It is unusual for a Court to make an Order for a step-child (or a child who is related to you) to be adopted as adoption is such a serious and final legal step.
This is partly because a Court can make a parenting order instead. A parenting order for a step-child can provide the step parent with parental responsibility for their step-child.
Adoption permanently severs the legal relationship between the child and their non-custodial parent and that parent’s family. For this reason, adoption orders in favour of a step parent are rare.
A legal relationship can be created however between a step parent and their step child without the Court having to make an Adoption Order.
The Court can make a parenting order which does give the relationship between the step parent and the step child legal status and so, a parenting order can meet the needs of both the step parent and the step child, without formal adoption having to occur.

Cant help you with advice but I am so happy for your daughter and you as well. Good luck