Well, figured out a solution (although not perfect)
eth0 was using automatic setting for IPV4+IPV6
after setting it to static, docker network br1 appeared and it's working (IPV4+IPV6).
eth1 is using automatic setting for IPV4+IPV6 so I didn't need to set addresses in docker settings (which is good because my IPV6 prefix isn't fixed, and a manual setting would not be valid after my prefix will change).
The only "problem" now is that Unraid GUI has two IP's in same subnet.