Its hard to tell if it was because of Akira's "transition" or just the fact living separately for work is not that uncommon there. (Maybe its both though)
But he doesnt seem out of Akira's life otherwise there would be no reason he'd show up for this and even try to get Akira clothes and asked her what she wanted to eat instead of just deciding on his own.
Still seems like a jackass, though the mom seemed in agreement about the backpack incident so...they both kind of suck.
I was a little confused too and I realized part of the confusion is the wording from some of the earlier chapters (or maybe just the translation choices?). In the character diagram on 37.5 it says the dad "abandoned" them and waaay back in chapter 6 when Akira is crying from having their first period Akira thinks it's their fault that their parents "split" and that the dad blamed the mom for what happened.
The dad is low key even worse in the pre serialized version and that one also gave it much more the vibe that Akira and Mom left suddenly rather than it being more ambiguiously amicable.
I kinda wonder if the author originally had the dad written out entirely but then retconned him back in? Maybe to use for some story beat later? Ig in the story world it's been 5-6 years at this point so maybe they're supposed to have sorta reconciled already, but you'd expect they make an arc out of that so maybe they are saving it for when Akira does finally open up to their mom.
But I know I wasn't going crazy when my first reaction to seeing the dad was "didn't this mfer straight up leave already?"