Granblue fantasy

Is GBF like SW, available on both PC and mobile?

There is a Chrome version.

And can accounts be linked?

If you mean the Google account, then yes. It's almost required.

And what gender should the champion be? I like playing as male characters, but I understand that to get Azazel's attention, it's better to play as a female?

Whatever you want. Besides, Gran is more of a default character than Dita. You can change the gender at any time, without restrictions. During events like these, I do exactly that. And in other places, gender almost doesn't affect flirting. Except, sometimes there might be a comment like, "How did you mistake me for your husband if I'm a girl?". The only exception, as far as I know, is one of the scenes with Vera, where the romance only goes towards a female character.

And like SW, is the game free-to-play, but with donations?

Yes, but you can only donate through mobile.