I couldn't tell you why this is the first thing that came to my head, but there's this 1999 Canadian movie called Top of the Food Chain which is this dry surreal parody of sci-fi B-movies; bisexual protagonist who ends up in a poly relationship at some point, with one of his partners being male and they have a pretty high amount of romantic scenes iirc
You can watch it on YouTube
Speaking of older gay Canadian content, I really wish I could be the one to recommend you a specific Bruce LaBruce movie. The thing is that I haven't gone deep enough in his filmography to lob you something from him, though feel more than welcome to check out his material for yourself. I heard it's some real good shit
Edit: Almost forgot about Strangers with Candy if you don't mind TV shows (though there's a prequel movie too)
There's always debate about which parts aged worse than others but I think the main couple of the show is pretty sensitively portrayed for a 1999 dark-ish comedy
The Wet Hot American Summer movie + TV shows + comic + radio drama (?!) also have a canonically gay couple that's depicted quite nicely