How can I prevent my loved one from just urinating anywhere in the house (on floor, in laundry basket, etc?) It is getting worse.

You can prevent the "loved one" from unrinating all over the place by placing them in the memory care facility they need to be in.

When someone is whipping it out and pissing anywhere and everywhere that is when it's time to find a residential care facility for them.

At this point your LO doesn't know what they are doing at all - Someone needs to keep an eye on them 24/7 to prevent this. Sounds like a disposable diaper won't work either because they remove their clothing! Tough one! Sorry I couldn't be more help. My only thought is to be on constant watch (like a baby or toddler) and at night I'd place a bed alarm so you know they're getting up! Maybe a bedside commode would work for that? My Best Wishes to You!

For me, this is now the time they need to be placed. For me, incontinence is the deal breaker.

You are dealing with dementia .
He can no longer be left to use the bathroom himself.
Every 2 hours at least you or someone needs to say.."Jack", it is time to go to the bathroom." and that person helps "Jack" up and walks him to the bathroom. And if need be you stand there until Jack is done, remind him to wash hands then say "Jack, let's go get something to drink" and go to the kitchen.
Doing this does a few things. Not only does it get him to the bathroom but it gets him moving, changes his position so that it help prevent pressure sores.

Change the type of clothing he has to a type that is more difficult for him to get off easily.

Signs are NOT going to work.
He may not know what the sign means any more, he may not know what a "bathroom" is he may not know how to read any more. Lots of reasons why signs will not work.

It is possible that you may have to look into placing him in Memory Care. this is a difficult decision but sometimes it gets to the point where the level of care necessary is more than can be done by 1 person at home.
It is not a "failure" it just means that his care is more than you can handle at home.

Adaptive clothing for people with dementia, such as an "anti-strip" jumpsuit so they can't take off their clothes without your help.

https://www.silverts.com/all-adaptive/pants/alzheimer-s-jumpsuits

Someone obviously needs to be with him 24/7, and needs to be taking him to the bathroom on a regular schedule(every 2 hours)and standing with him to make sure he's peeing in the toilet and not elsewhere.
If that can't be done in home, then placement in a memory care facility is the next step.

Sounds like mom needs more care, have you considered memory care?

Your moms brain is broke it's only going to get worse. It might be time to start thinking about future care for her

I don't really have any good ideas on how to stop that. Other than a onesie. Which I think they do make for adults, which you can check on Amazon.

Best of luck, Im sure this is very hard 🙏

24/7 close supervision or contain the urine.

If the person can feel the urge it would be nicer for them to go in the appropriate place - but if they cannot, I can only think of 2 solutions;
1. Complete, close supervision,
then assistance to quickly move to the bathroom (or urinal bottle)
2. Incontinence underwear (pullups) + anti-strip clothing