I recommand to replace the default bridge with a 'user bridge'.
The 'user bridge' is more powerful and safer than the 'default bridge' as the official docker document describe:
Use the default bridge network
The next version Unraid can consider to create a default 'user bridge' with network: 172.18.0.0/16 (disable the old/default 'bridge' network 172.17.0.0/16) on initialized installation and generate an unused ip address automatically when a new docker container is created. It also allow user to assign an IP for a container within the 172.18.0.x.