You shouldn’t incus remote switch to an image server as otherwise it will try to create the instance on the image server, failing with the error you’re getting.
So run incus remote switch local to be back to your local system.
That said, I expect incus image list ubuntu: to be empty as the Ubuntu image servers don’t publish images with the Incus metadata.
You can manually go to Ubuntu 22.04 LTS (Jammy Jellyfish) release [20240319], then download ubuntu-22.04-server-cloudimg-amd64.squashfs and ubuntu-22.04-server-cloudimg-amd64-lxd.tar.xz and then manually import those locally with:
incus image import --alias ubuntu-2204 ubuntu-22.04-server-cloudimg-amd64-lxd.tar.xz ubuntu-22.04-server-cloudimg-amd64.squashfs
After which you can do:
incus launch ubuntu2204 ubuntu-jammy