LimeSDR USB and Mode-S/ADS-B

Hopefully this isn’t a silly question; I’m new to SDR and the LimeSDR.

I’m trying to use rx_modes to receive ADS-B traffic with the LimeSDR USB, but I’m having no success (I either get garbage, or nothing at all - but mostly garbage). I’m running the following:

modes_rx --source=osmocom --args=driver=lime,soapy=0 --antenna=LNAL

(if I replace --antenna=LNAL with --antenna=NONE, I still get garbage which suggests something is fundamentally not working at all).

I know the LimeSDR is basically working: if I run osmocom_fft --args=driver=lime,soapy=0 --antenna=LNAL, set it to (say) 433.45MHz and key up my handheld radio, I see my handheld getting keyed just fine on the FFT display or waterfall, and the various GUI controls do what I would expect them to do. I can also use SDRAngel to transmit and receive without any problems.

I’ve also struggled to find out what arguments can be added to --args=driver=lime,soapy=0 - running SoapySDRUtil --probe=“driver=lime” shows a lot of options that should be settable, but my Google-fu doesn’t seem strong enough to actually find a list of valid keywords (and knowing that they are set - I can put obvious garbage in that args= line and get no errors or warnings).