SFDX: How to change org's alias?

You can use force:alias:set:

sfdx force:alias:set [email protected]

The original alias is automatically removed/renamed with this command.

It looks like the alias commands have moved from being under the force namespace to being in their own namespace.

https://developer.salesforce.com/docs/atlas.en-us.sfdx_cli_reference.meta/sfdx_cli_reference/cli_reference_alias_set.htm

sfdx alias:set [email protected]