services.graylog.depends_on contains an invalid type, it should be an array

[litecactus]

While running docker-compose up I see an error, perhaps a formatting issue?

me@graylog:~/graylog$ docker-compose up
ERROR: The Compose file './docker-compose.yml' is invalid because:
services.graylog.depends_on contains an invalid type, it should be an array

[litecactus]

Changing docker-compose version from "3" to "2.2" seems to do the trick and get it to run, after researching, the depends_on was removed from v3. Need to do more research to discover the correct syntax for v3. Perhaps someone who knows more can chip in here?

Seems to work fine on my system. Try using compose V2. I see you're running docker-compose (note the hyphen) and not docker compose like stated in the readme.
See: https://docs.docker.com/compose/migrate/

[litecactus]

OK so yeah using docker compose and setting version: '3' works. I had docker.io installed so I removed that and installed docker-ce via the docker install instructions on https://docs.docker.com/engine/install/ubuntu/ rather than just using apt install docker.

So if anyone runs into this issue, follow the install instructions for your environment directly from docker and don't use apt.