The Serengeti has a cluster of public campsites around Seronera with simple shared ablution blocks and no fixed infrastructure beyond that. They're used mainly by camping safaris where a crew travels with you and sets up tents, cooks and breaks camp each day. Nights are genuinely wild — you're in the open park, with hyena and the occasional lion passing through.
This is the budget end of a Serengeti safari and the trade-off is comfort, not access: you're in exactly the same part of the park as guests paying ten times as much.