Piaware SD card image 3.8.0 (Buster) by default behaves as 1090 mhz only, though it has 978 mhz builtin, but 978mhz is inactive by default.
If you want to run 978mhz also, you will need 2nd dongle+antenna set to plug into RPi for 978mhz, serialize the two dongles, and issue few commands to activate 978mhz.