...How does her transness work in this medievalish setting?
I know this is a tad 'nitpicky' but..
'Trans' is short for 'transitioning'
Since (from what I've garnered from the story) she was born that way, 'trans' doesn't really apply.
Futa is the term many would use, but that's not exactly right either.
Futanari is Japanese for Hermaphrodite (meaning both genders, XXY)
And she's not that either. No vagina.
The term which I would use is Dick-girl.
Is there some kind of magical/herbal/fantasy hormone replacement therapy in Your world
...
There *is* magic in this world.
It's not been really brought to the front (yet) in the story.
Early in the 1st chapter, MC can't understand Beardo. Beardo puts his hands on MCs throat, sparkly blue lights, narrator quips about 'magical contrivances', MC can now understand Beardo.
So... anything goes.
Also,
Keep in mind her name is Astrid Nofadir (No father).
In a medieval setting such a surname would be common enough for the child of a 'harlot' who's father was unknown.
But, since there *is* magic in this world, it
might be literal. She actually doesn't have a father.
Maybe she is a being brought into existence through magic.
A 'Chosen One'
I know she is
my Chosen One