In my experience, if you don't know someone's pronouns, it's best to use they/them until you find out
That way you don't get a specific gender in your head and it's easier to switch to using their pronouns
IT DOESN'T MATTER WHO YOU ARE; WHO YOU ARE ATTRACTED TO; WHO YOU LOVE; WHO YOU DATE; WHO YOU MARRY; WHAT YOU IDENTIFY AS; WHO YOU ARE FRIENDS WITH; OR ANYTHING LIKE THAT; WE ARE ALL UNITED BY THE PRONOUNS "THEY" AND "THEM"