Same for me.
On one host it correctly binds to IPv6 and IPv4, and on another it only binds to IPv4.
Hosts have a plain vanilla Debian 10 install, and docker and docker-compose have been installed from the official repositories provided by Docker; they have perfectly working dual IPv4-IPv6 stack. Same environment (basically it is working on our test machine but not in production!)
I can verify with ss -tlnp.
On one host (not working, let’s call it V):
LISTEN 0 128 0.0.0.0:3022 0.0.0.0:* users:(("docker-proxy",pid=1571,fd=4))
On the other host (correctly working, let’s call it A):
LISTEN 0 128 *:3000 *:* users:(("docker-proxy",pid=4762,fd=4))
I tried to force binding to my IPv6 in ports option, but it looks like IPv6 binding isn’t supported yet in 2021!
Everywhere online it looks like people are facing the opposite issue (eg. docker binds to IPv6 only). If only it was true! 
Any help is appreciated. Thank you.