it doesnot look Celtic at all due to UK spread where it looks as a force opposing/conquering Celtic settlements from east towards west...
its either Germanic or it spread with Romans..
its unlikely that we would see Romanic settlements in Ireland or in UK north from Hadrian's wall, so Romanic spread is also questionable.
furthermore it is strong in parts of Germany that were never part of Roman empire...
so it looks mostly germanic to me...
imprint on UK looks more germanic than celtic
Iberia hotspots match Suebi and Vandals..
Vandals being pushed by conquering Visigoths somewhat to west and also to south to north Africa (see rightmost picture showing kingdom of Vandals in north Africa, Sardinia and Sicily) and note some spread present in north Africa, Sardinia and Sicily as well)
from Germany to France could be spread by Franks.. note here that Corsica with high spread was part of frankish kingdom while neighbouring Sardinia with low spread was not part of Frankish kingdom..
note that north Italy, Croatia and Slovenia with somewhat elevated spread were as well parts of frankish kingdom..note that Vasconia which was not integral part of frankish kingdom has low spread as well
north Italy was also conquered and settled by several Germanic tribes..
Asia minor, Greece, Romania and Albania is original starting point of the spread 3-5000 years ago ..as witnessed by older R1b (see the map of ht35 bellow) and also by myth of origin of Franks that relates them to Asia minor and Troy (
https://en.wikipedia.org/wiki/Franks#Mythological_origins)
spread from Asia minor suggests that Etruscans carried it as welll (not necesserilly as dominant)...
north Italy is thus explained as multiple waves of settlement...first Etruscans later Lombards, Franks and others..
for instance R-Z56 being spread by people from Asia minor mostly Etruscan, R-L2 spread by Franks and Vandals and R-Z36 by Langobards
Etruscans
Lombardy