With the new syntax changes, the display-Name tag works correctly, but display-LocName no longer works to change the item's name.
This command works:
/give @p stone{display:{Name:"{\"text\":\"Rock\"}"}}
However, this command will only give an untampered stone block
/give @p stone{display:{LocName:"{\"text\":\"Rock\"}"}}
Linked issues
Comments

It looks like the recent component changes included deprecating
LocName
; instead, you should specify atranslate
component. (There is an upgrade path that will automatically do this for old worlds, but it doesn't change commands).Note that using
LocName
with something that isn't a translation string is not the intended use.If your goal is to make the text not italic, please see MC-123790.