Since the ADSB Exchange Blue R820T2 RTL2832U, 0.5 PPM TCXO ADS-B SDR w/Amp and 1090 Mhz Filter is not available, what is the option for Raspberry Pi replacement?
@CommGuy stated on Discord that stock of ADSBx blue sticks is on its way to Amazon this week.
Other options might include the FlightAware blue stick, which is essentially the same, except it has a plastic case, and the blue sticks found on AliExpress. No guarantees on either of those options here, but reports have suggested that they work equivalently.
Another option would be a generic RTL-SDR (blog type or NooElec, etc), with an external filtered LNA, like the Uputronics one, but that would be a pricier way to go…