I suspect state law does not regulate this one way or the other, but I have not checked.

"Can an owner provide a unisex multi-person restroom if they so chose?" - Gas stations all over the country are like this One restroom.

I've yet to see a unisex bathroom with a functional urinal. Most of the ones I see are either a single fixture bathroom with a lock, or two single fixture rest rooms (again with locks) that may have previously been divided into Male/Female but went unisex because in that situation, it's more efficient for a man to use the second restroom that's empty than force him to wait for the other man in the men's room to hurry up while the women go.

The only time I've heard of urinals not exclusively in men's rooms is in jobs that used to be almost exclusively men's restroom, was from my mother, who was one of the first women hired by by her office, which was in a traditionally male exclusive industry and had the lack of foresight to install facilities for women when the old building was built, so when they started hiring women, the converted some men's rooms into women's rooms by simply changing the signage. The urinals' were eventually removed, but until they were repurposed to be self-watering flower pots.

Also, there are quite a few unisex facilities in the U.S. that predate wider acceptance of Non-Binary and Transgendered people. More often than not, they were called "Family Restrooms" as they were functionally built for parents with small children of the opposite gender to use.

@WPNSGuy but those tend to not be multi person, ie multiple people are expected to be in the same restroom at the same time.

@hszmv it used to be quite common in bars in France. They could be rather cramped, to the extent that a man using the urinal could be standing back to back with a woman washing her hands. With more space, the urinal(s) might be behind a door - but often little saloon-bar half-doors

I've seen plenty of small businesses that have only one restroom marked "RESTROOM" or similar, with a lock on the inside to be used during occupancy. Requiring two sets of fixtures in two separate rooms would be daft.

@ArthurKalliokoski The question is about restroom which can accommodate several persons at the same time.

Like on Ally McBeal?

@MonkeyZeus I'm not convinced it's gender discrimination to offer something that benefits one sex so long as your are offering services to both, ie by having enough restrooms for all. Is an Ob\GYN discriminating for focusing on women? Is allowing driving licenses to some when we know others will not qualify for them due to disability? not discriminating doesn't mean we need to drag everyone down to the lowest common denominator by depriving others of what is most advantageous to them. If anything women should want urinals, if men are faster in the restroom that leaves less a line for them.

@ChrisH Oh, yeah, Americans would not like that at all. There's an unwritten rule in America that unless it's an emergency, you do not use any Urinal that is directly next to an occupied Urinal. Closest I've seen was in a gay club where the toilets were gender separated (though they didn't label them as such... one side of the partition had Urinals and Thrones, the other had Thrones) but the sinks were communal and outside of the patrician.

@dsollen You might be right and so might I; the average business will make the decision which loses them the least amount of customers. Have you ever tried asking a woman her thoughts on being in the same room as a urinal?

@MonkeyZeus That's a different issue, though I think the real problem is being in the same room as a man, after all most porta potties have urinals in them and while people don't like using them for other valid reasons I've never heard anyone cite the urinal as the problem. Realistically convincing people from the USA to use same sex, multi person, restrooms would be quite a challenge.

@hszmv that unwritten rule seems quite common; even with trough urinals maximising separation between users is usual