The current bug in FR24 feeder is its failure to connect to FR24 server if it tries IPv6 address. This is totally due to some bug in their servers. I am not sure if it is solved or still there.
If you face an error message of failure to connect, see the 2 bug-fixes given below
As a temporary measure, FR24 admin suggested to block IPv6 by giving this command
sudo sysctl -w net.ipv6.conf.all.disable_ipv6=1
However this command is to be re-issued at every reboot of Pi.
A FR24 forum member gave a better solution. Instead of totally blocking IPv6, he suggested following method to change preference to IPv4. I have tested it, and it works fine. Here is this method:
sudo nano /etc/gai.conf
In this file scroll down to find following line:
#precedence ::ffff:0:0/96 100
Uncomment this line so it looks like:
precedence ::ffff:0:0/96 100
Now Pi will prefer IPv4
sudo systemctl restart fr24feed