I’m so sorry to hear that your family won’t be attending your wedding.
DF and I have discussed this and we’re thinking of doing one of two options, both of which involve the two of us greeting the guests at the doors of the church:
In one option our parents are seated and we walk in together.
In the other option we each process in accompanied by both of our parents.
I personally prefer the first option. My dad will be there and we’re close, but we don’t have the kind of father/daughter relationship where either of us would be heartbroken by breaking with “tradition.”
So as PPs said, you can walk by yourself, walk with DF or perhaps find someone who is like a father figure to you to accompany you down the aisle.