Mattermost docker image for redhat

No, there shouldn't need to be a separate image for redhat. Not sure why it wouldn't build there. To debug that I would need more info.

However if you just want to get it running, you should be able to run the command
docker run --name mattermost-preview -d --publish 8065:8065 mattermost/mattermost-preview
to do that. More info can be found in the docs here: https://docs.mattermost.com/install/docker-local-machine.html