As a full-time RVer (or just someone planning a long cross-country RV trip) you may have considered staying overnight in a Walmart parking lot.
True, Walmart parking appears on many RVing apps, but it is best to call to discuss your stop with a store employee.
Taking more space than necessary or blocking space for other RVers and truckers is, simply put, very rude.
Try to arrive late in the day, after the Walmart rush. After you arrive on-site, again talk to the store manager.
Over the past years, several county or city ordinances have been enacted to disallow overnight RV parking in Walmart lots.