I am FTM trans and my wife is not :)
We are in Canada and legally married before I transitioned.
I kept my last name and she kept her last name.
Our DD has my last name and my DW's last name as a second middle name.
My wife carried and birthed our DD and I do not have any biological connection to our DD. It was important for my wife to give the child my last name to make me feel more connected to the child. For me I didn't worry about feeling connected to the child. I am very connected to her. But I did want the last name to be mine so that other people would see me connected to the child. I didn't want other to think of me as the step father (when she gets to school age etc) and I liked the little bit of added legal protection it makes me feel I have.
I am also from Ontario, and we used a non-known donor, so I am legally the second parent on the birth registry and never had to do a second parent adoption to be the legal parent of my child.