Currently (as on 2021-04-28), arduino-esp32 support ESP32-S2 and ESP32-C3 in development release 2.0.0-alpha1.
To install development release to Arduino IDE board manager:
Click in Arduino IDE Menu > File > Preferences
Enter development release link () in Additional Boards Manager URLs:
Open board manager:
Tools > Board > Boards Manager
Search and select esp32 by Esoressif systems, install the latest version, currentlt 2.0.0-alpha1.
After then, ESP32C3/ESP32S2 Dev Modules are available in board list.