Not personally tested yet, but looks very useful and promising.
Introduction
ESP-WIFI-MESH | Espressif Systems
Web app for testing
ESP-Mesh Resources | Espressif Systems
Practical example
ESP32 #84: ESP-MESH MESH and ESP-MDF – YouTube
Github repository
GitHub – espressif/esp-mdf: Espressif Mesh Development Framework
Comparison between ESP-NOW and Lora including power consumption.
Example with painless mesh. Some issues are mentioned in the comment.
ESP-MESH with ESP32 and ESP8266: Getting Started | Random Nerd Tutorials
ESP32 Mesh Network