Did you run the image as shown in github (/home/example should point to a valid directory in your host)?
docker run -it --rm -p 80:80 -v /home/example:/data -v /var/run/docker.sock:/var/run/docker.sock --pid=host --stop-timeout 60 dockurr/umbrel
The -p 80:80 option configures the bridge between your host and your container. Can you show the ouptup of the command docker ps?
NOTE: Once everything is working, you can run the container in daemon mode (-d instead of -it):
docker run -d --rm -p 80:80 -v /home/example:/data -v /var/run/docker.sock:/var/run/docker.sock --pid=host --stop-timeout 60 dockurr/umbrel