The apps on line of Dump Station Location Listings are the least accurate of RV info IMO. Just not kept up to date as much as possible. Gov't ran dump sites are most dependable to be operational, but still verify by phone if possible. Many rest stops have shut there's down because of mis-use. When traveling, my LED light on my tank level gauge lights up to 3/4 I start looking.
For close to home...Explore your area and find what's best for you. Many sites are not listed. As it turned out, closest to me was an "Eagles campground". Less than 2 miles away and never a line. $10 bucks and includes getting a beer inside. I mentioned I was going to add the site to an on app. They preferred not because of experiences in the past they had with the general public. My inlaws use a rv storage place that has a dump site for their customers, but lets "locals" use if they know about it.