I disagree that Gran is "canon", because it makes no sense in this series (and I don't like the term, anyway, since it's fiction to begin with). The anime is clearly not connected with the game, the PS4 game is confirmed to be an alternate reality than the mobile game, so what makes Gran's journey the canon one? It's just different stories.
But yeah, he's the default protagonist, and I wish they would change the start of the game so we can start with Djeeta as well, but I guess they're too lazy for that.
Funny thing is that Djeeta is the most popular character, being the one most used by players. So the decision in using Gran is just a stupid tendency to be traditional.
On the yuri side, beside all said above, there's some character who have a interest in the protagonist, and it doesn't change if you're playing with Djeeta or Gran. So there's some girls who'll be into Djeeta (Zeta being one of them)...as well as at least on guy who flirts with Gran. On the other side, the events with Vira as shown to be more romantic towards the player when you're playing with Djeeta than when you're playing with Gran.
There's also Cordelia, the girl who looks like a handsome man (not at all), and all the girls are in love with her. She has a female friend that knows she's a girl and all the events the two of them are together, they're always flirting with each other.
Some other yuri pairings too, like Silvia and Song (player who saw her 5 star uncap says they're basically a couple) and Yuel and Societte.
It's a fun game, if not a little grind. But the story are really well written, so even if you're not playing it for the gameplay, it's worth to keep coming back to each event.
Also, next two anime episodes will probably be an alternate story with Djeeta as protagonist. It's a shame she gets only that, but at least it's something.