Removing all login IP restrictions on a profile in the sandbox via Metadata (removing all the login IP sections in the XML) and saving the file, but the change isn't reflected in the org.
The docs at https://developer.salesforce.com/docs/atlas.en-us.api_meta.meta/api_meta/meta_profile.htm state (with my emphasis)
To delete login hour restrictions from a profile that previously had them, you must explicitly include an empty loginHours tag without any start or end times.
Could the same be true of login IP restrictions as well? The doc doesn't explicitly say so, but it would largely make sense that it worked in a consistent way