How old would you say are the European ethnicities?

That is, what length of time have modern ethnic groups been essentially the same people and distinct, primarily genetically + identity/culture wise?

IMO:

English: at least 1300 years, since the time of Bede
Scottish: 1000-1100 years
Welsh: Antiquity as British, 1500 years as specifically Welsh/Cymric
Irish: Antiquity, up to 4000 years potentially
Germans: Antiquity, perhaps 2300 years, after they spread South into Celtic lands.
Dutch: under 500 years? Maybe a few centuries older as Netherlandish.
White Americans: 250-300 years (Old Stock), perhaps less than a century for modern White Americans overall.
White Australians: 100-200 years for Anglo-Celtic white Australians.
Greeks: Bronze Age, 4-5000 years?

French is tough to say, but I wouldn't put it back as far as Gallic times, nor as recently as the French revolution.

As you reiterated very succinctly, Europeans were more tribal in nature before nationalistic, modern day terms came into fruition. After the dissolution of Empires, Monarchy, eventual collapse of conjoined nation-states; it wasn't until recently European nationalities gained prominence after the rising interest in capitalistic, self-autonomous countries in our globalized economy today that gained momentum during the Industrial Revolution era and onwards.

General Speaking, I would say between 1000 to 1930 C.E. when European countries formed their nationalities during the formation of their Kingdoms and for others, during the collapse of Empires such as Austria-Hungary, Holy Roman Empire, etc.