South rim Grand Canyon

you are so close, try for Four Corners and monument valley too:B

There were half a dozen RV's at a Flagstaff Wal-Mart about 9pm this past September. The location was the one on the east side of Flagstaff. Call and ask the store.

If you’re up for “boondocking”, the ultimate social distancing”..... there some very nice camping spots along some “forest service roads” just out of ( we stayed down road #302) Tusayan. We found a “two-track” which took us about 600 to 800 yards off of road #302....It was dust free, very pretty, quiet, and offered great “social distancing” .....except for the little bunch of elk that passed through! It was a nice, open, smooth “two-track” road, which worked well with our 40 foot 5th wheel.

If you have an iPhone, there is an app, “ALLSTAYS”, which is a pretty handy source of “boondocking” / free camping locations! memtb

Note that you'll want to check the Grand Canyon NPS website for current information. They just did a very limited opening last week (south entrance only, practically no services, limited viewpoints open, etc.) Already they just closed right now for three days, and website indicates to stay tuned for info about Memorial Day weekend. So things keep changing.

I'd probably overnight on USFS land (or Ten-X campground, if open) just south of Tusayan.

Thank you all.

There is dispersed camping in the area as well as a couple of private parks.
Check this
RV parky
Maybe this will help.

There's a Cracker Barrel in Flagstaff that allows overnight parking.

According to RVParkey.
2 Walmarts in Flagstaff, do not allow overnight parking.
The Walmart in Page does allow overnight parking.

Nearest Walmarts are probably Flagstaff or Page. Not sure if they allow overnight parking any more. They did 9 years ago, last time we needed a freebee.
Nearest "free" parking I can think of at the east entrance (might be on Navajo Reservation currently closed?) might be a gas station in Cameron. Other one I'm aware of is a USFS road at the south end of Tusayan. Or the GC airport? There are some roads in the area that may have BLM camping, but I've never used any of it. We just stay in the park usually.