LinkFieldFactory$ChooseDialogCallback#onItemChosen is fishy at best. In particular, LinkFieldDefinition's targetPropertyToPopulate property is unclear, undocumented, most likely unused and should be deprecated. It strongly looks like legacy code pre-transformers and pre-identifierToPathConverter—which I'd expect to be used in that callback method instead.

At the moment, plain LinkFieldDefinition cannot be used with resources app in 5.4, because of this.

As a workaround, one may use a custom LinkFieldFactory for resources app, as shown at https://git.magnolia-cms.com/projects/modules/repos/resources/commits/1e662634b1243f44242d9f321ca9a75a1354e30b