Thanks for this, I'll save this info for the future.
For me, running dump978-fa, I only had to do the following to start feeding RB24 without using their built-in dump978:
Edit rbfeeder.ini
sudo nano /etc/rbfeeder.ini
Change the 1st part under [dump978] section to true. Add the 2nd line. Save.
[dump978]
dump978_enabled=true
dump978_port=30979
Restart the rbfeeder
sudo systemctl restart rbfeeder
Did not edit /etc/default/dump978-fa but it looks like this:
ENABLED=yes
RECEIVER_OPTIONS="--raw-port 30978 --json-port 30979 --sdr-gain 40.2 --sdr driver=rtlsdr,serial=00000978"
In addition to RB24, feed 978 data to FA, FR24, and ADSBx.
YMMV!