It's not visible due to privacy but on my profile I've used the date we got together and wrote not married.in the place field.
Bit of a bodge but I've seen other people put married or mistress in the marriage field. We've been together for 24 years, have three kids, been faithful, it's functionally a marriage.
Gay guy I know got married. It's not legally recognised but he had a big wedding and all the rest. He's got a date and place but, as per comments below, would we really not enter it because it wasn't Court recognised?
Sure the details can be put in the biography, but they can be missed there.
If guess there's a question of where do you draw the line, and it's not like I think I'm suggesting adding every last girlfriend and boyfriend is fine, but 27 years is married as far as I'm concerned.