What is the way to find programmatically a reference of a field in different metadata like flows, LWC, aura etc?

Leonardo Kipper (KCS iT) is right. sfdc-soup is very used.

Salesforce provides only MetadataComponentDependency (Beta) (quite old object now and still "beta").

It is easy to query MetadataComponentDependency with SOQL (tooling) but the fields are not clear for their names (missing extension __c) and sfdc-soup remains clearer.

https://developer.salesforce.com/docs/atlas.en-us.api_tooling.meta/api_tooling/tooling_api_objects_metadatacomponentdependency.htm

https://trailhead.salesforce.com/fr/trailblazer-community/groups/0F93A00000020Vu?tab=discussion&sort=LAST_MODIFIED_DATE_DESC