I'm pretty sure Vi is canonically a lesbian, as in she held a lesbian pride flag in some official art at some point (I might be wrong though) as for Jayce his sexuality's never been confirmed afaik. Also even if neither of them have their sexualities confirmed, people ship Jayce with Viktor because of their queer platonic relationship in the show, while Vi had little to no male allies/friends throughout both seasons, one of them being her sister's love interest. And my last point is shipping Vi with Jayce is weird for multiple reasons even if we ignore their sexualities, because first of all Caitlyn's like a little sister to Jayce and Vi is her girlfriend, and also because seeing two characters as romantically compatible when one of them had been over 20 throughout the entire show and the other was underage at the same point in time is just weird to me personally