Cannot run apt-get update in docker

I am having issues connecting with apt-get from a Docker image. To recreate, I can run

sudo docker run -it ubuntu /bin/bash

and then type:

apt-get update

Without fail, the machine is unable to connect and I get a series of errors that look like this:

Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal/InRelease Could not connect to ports.ubuntu.com:80 (91.189.88.152), connection timed out

I am running an M1 Macbook Pro and have tried:

• Changing DNS settings
• Other docker base images
• I'm able to successfully download from other sources (eg. pip install)
• Disabling IPv6
• Trying another wi-fi network (I'm not behind any firewalls)

None of this has helped so far, and I have been completely unable to apt-get update or apt-get install to work in a docker container. Would greatly appreciate the help!