21. Why FiiO Control doesn't show available Aptx Lossless codec?

aptX Lossless is belong to aptX Adaptive, the firmware has enabled aptX Adaptive and supported aptX Lossless by default   ( App control does not need to adjust the encoding, just keep the aptX Adaptive option ticked )

If the phone supports aptX Lossless, connect BTR17 to it and BTR17 will show aptX LS.