Note that "international First Class" on DL is identical to it's domestic First Class product/service. DL ditched it's traditional international First Class many years ago (while still being offered on a few partners like AF and KE). They did continue to offer lounge access on DL international FC flights (excluding Caribbean) up until around the end of 2018 before limited it to Delta One marketed flights only (unless you had DL STE+ status which continued to provide Sky Club access on international flights in all classes of service except for Caribbean flights).