Certain casinos show the fights. For example, there's a place called Moneyline Sports Bar inside of the Park MGM that shows the fights -- I watched the March 6 card at Moneyline. Usually, I go to Miller's Ale House, but Miller's is closed for good, due to the pandemic draining all of their money and not being able to financially recover. I will look for a place to watch UFC 250 when I land on Thursday, June 4.
Use this link to find where UFC events are shown in Vegas (you can click on Confirmed and Unconfirmed -- there's usually 20+ places that show UFC events, but the map isn't updated due to Vegas not reopening until June 4):
https://bars.ufc.com/bars-in/NV
I'll post the direct link to the next event (UFC 250), then you can try joining it.