The latest firmware is usually designed for ATS-20+ V2 boards.
via USB-C, put the device in flash mode (usually by holding the encoder knob while powering on), and upload the new firmware. Comparison: Stock vs. Exclusive Firmware Stock Firmware Exclusive/Updated Firmware Basic, noisy Smooth, refined AGC Handling Aggressive, soft-mute Optimized, stable BFO Adjustment Fine (Step control) Band Scanning Faster, more responsive Filter Selection Broad (up to 4kHz) Conclusion The ATS-20 SI4732 ats20 firmware exclusive