Docker daemon.json Proxy Settings Require Engine 23 or Later
Check the daemon version when proxy fields copied into daemon.json are unsupported, and use the service environment appropriate to older native Engine releases.
Docker Engine 23.0 introduced daemon proxy configuration through JSON and command-line flags. An older daemon cannot use those fields simply because the current documentation shows them.
Check the server version of the daemon being administered. The CLI version, distribution name and container image tag do not establish that server's feature set.
For an older native Linux Engine managed by systemd, supply HTTP_PROXY, HTTPS_PROXY and intended NO_PROXY through the daemon service's supported startup environment. Exporting them in the terminal running docker pull does not update an already running system service.
If retaining the older Engine, use that supported method. If upgrading, reconcile old environment values with the daemon configuration: direct configuration takes precedence over environment variables in current Docker documentation, so conflicting values can change the selected route.
Docker Desktop uses its own proxy settings and ignores daemon proxy entries in daemon.json. Identify that product before applying a native Linux daemon workaround.