Do you need to sand an osb subfloor before putting a sealer on it?????

You need to make sure the area is very clean before you do whatever you are going to do. My son laid a vinyl plank flooring in his mobile home last year and it looks great, very inexpensive also. Very durable too.

https://www.doityourself.com/stry/how-to-waterproof-your-osb

As a previous owner of 16 rental mobile homes, I can tell you that the cheaper ones are sold new with osb or particleboard as a subfloor. Problem with that is that, like particle board, osb swells up and crumbles when exposed to moisture and water leaks. And since water leaks and excessive moisture from the bottom of the trailer are 2 very common problems with trailers in general, I would NEVER EVER advise you to cover the osb with anything more costly than the cheapest of cheap linoleum. This is especially true if you are a renter. If you own the home, the smart solution is to save a little money every month in a jar labeled "Treated Plywood". Eventually you will have enough to buy some 3/4" 4'x8' sheets of weather-treated plywood. Then, one room at a time, pull out the osb and replace with the real plywood. Just make sure you buy weather-treated. This is a DIY job that goes faster if you have a young, strong (and preferably good-looking) friend who is nice enough (stupid enough) to work for pizza and beer. The plywood sub-floor will increase the value of the trailer if you sell one day. And in the meantime you will not risk seeing your bathtub or toilet or refrig fall through the floor to the ground due to an unseen water leak! Sealing the osb will create a big mess ( due to sanding dust throughout the whole house), and you will never get it nice and smooth the way you would want it if you're going to the trouble of sanding it in the first place! The sandpaper and a good polyurethene will be pretty costly, and I guarantee you it will be very work intensive. In addition the rental cost of a good floor sander is ridiculous. It would not be a cheap thing to do, and the aesthetic results would not be good. You've been living with it as is until now. So if you are a renter, buy a really cheap room sized rug online to cover up the ugly subfloor, and you can take it with you when you move. This is a good solution even for the kitchen or bathroom floor. And if you own the home, a rug will make it look and feel better underfoot till you save up enough money to replace the subfloor (then saving again for some nice flooring to top off the plywood). I'm jus sayin

I would imagine that this type of flooring does not require sanding before sealing