Would've liked to have known that Syd was aro before I got invested several years ago. I'm personally not interested in 'romancing' a character who can't reciprocate the MC's feelings.
Agreed there, personally I was quite invested in that relationship, the entire S2 felt like peak fiction chasing after her but just the begining of chapter 3 really rather ruined it for me :X Very dissapointing from my point of view.
Its the writers business of course and she is a great character besides, but yea, knowing that the relationship is generally impossible to exist in the proper sense of the word makes it weird that she is labeled as "romanceable".
I had hoped that there was more to it, even after I read the start of Season 3 but it was confirmed by the writer so thats just that. Nothing against writing such a character but I agree that it should be made clear to the reader in advance, otherwise I would have absolutely adored this romance, as is, it just cant really be called that.
That she is aromantic, meaning she cant be romantically attracted to others. I have spoken to the writer on tumblr (I believe, its been a while but I think it was there) and he/she confirmed that Sydero is aromantic, quite dissapointing tbh, especially as there was a ton of other ways her relationship issues could have been explained. But what can you do.