Normally you should be able to use dump1090-fa as a relay for the data.
But you can’t modify the main dump1090-fa configuration file on a piaware sd-card installation.
So you need to run a 2nd dump1090-fa for which you can change the settings.
Edit: For piaware sd-card you can run a 2nd dump1090-fa independently, for example with combine1090:
Install it and open the configuration as shown on the github page.
Change the target to localhost:29001
TARGET=127.0.0.1:29001
Modify source and port accordingly to where your microadsb receiver is offering AVR data.
SOURCES=192.168.2.44
(Ip address where your microADSB is offering data
PORTS=30002
Make sure the settings are active:
sudo systemctl restart combine1090
Point piaware at localhost:29005 for the beast data.
sudo piaware-config receiver-host localhost
sudo piaware-config receiver-port 29005