You can get a SpeedyBee AIO board at a decent price.
The SpeedyBee AIO - F4 FC + 40A 3-6S 4-in-1 Bluejay ESC combines a high-performance STM32F405 flight controller with a 40A ESC, supporting 3-6S LiPo batteries and DSHOT600/300 protocols.
www.getfpv.com
It will run all the "main" firmwares. INAV, BetaFlight, Ardupilot