Very few characters are presented as having more than one romantic interest, with most of the exceptions being generally promiscuous. So of course the most visibly bi characters will often be promiscuous ones.

One notable exception is the story in https://en.uesp.net/wiki/Online:A_Change_of_Heart Unfortunately for this discussion, that's basically a combat + mystery quest. When the mystery is resolved, it turns out there are LGBT+ and social-class issues to address, but dealing with them is rather rushed.