I refer to Angela's last post, which I subscribe to 100%.
In fact it is always Polybius (II, 19-21) who remembers that it was Gaius Flaminius's policy of massive colonization in the northern Marche region that alarmed the Boi who, fearing the same fate as their Senones neighbors, turned out to be quite hostile towards Rome.
https://www.gutenberg.org/files/44125/44125-h/44125-h.htm
http://docenti.unimc.it/simone.sisani/teaching/2016/16254/files/Storia Romana_5.pdf
I believe that with regard to the Insubres, the Cenomans and other transpadane populations in general, the Romans of a later generation were more wary, even with more practical policies of local military recruitment and subsequent granting of Roman citizenship, precisely in order not to trigger reactions to chain that would become less and less controllable as they left Rome.
That those territories, now corresponding more or less to the province of Pesaro-Urbino and to the entire Emilia-Romagna region, have been the object of an important Roman-Italic colonization is beyond doubt (in fact all the cities and centers along the Via Emilia have been Roman colonies). The Emilians and even more so the Romagnols, compared to their present Lombardi neighbors, emphasized in their autosomal - of some point - Caucasian and Mediterranean-eastern components that could very well be attributed to the arrival of Central Italic settlers.
However, I have always had many doubts about the total expulsion of Senoni and Boi from the Picenus and Po valley. In the first place, from the dialectal point of view, these are territories that remained Gallo-Italic in all respects, with very marginal external influences (in the province of Pesaro, the dialect is a variety of Romagna), where the general rule is a Latin that merges with a Celtic substrate. Some substantial pouch still had to be present.
What sense would the persistence of a language (or of such an important linguistic phenomenon) be due to a people decimated, vanquished, marginalized or even expelled?
Another hypothesis that I would like to advance is a supposition of mine born in relation to the 23andMe tool, Your DNA Family.
Given that in Italy this kind of test is still little known and adopted while it is widespread in the USA, UK, Canada, (so we are talking about statistics that are not significant on the one hand and overrepresented on the other), it remains to ask why someone like me - a matter of fact of areas of eastern Emilia/Romagna where the Gallic influence was already diluted in Antiquity, due to Etruscan, Umbrian and Greek strong coexistence and which clearly underwent Roman domination - it is found, however, at the top of the rankings respectively 87 % of genetic cousins with Franco-German ancestral origins and another 85% with British origins? (For the moment my Italians are 28%). Keep in mind that I'm not talking about Italian-Americans and / or Italian-British, so individuals who do not bear Italian origins.
For now, in my opinion, the only possibility is to admit that even after the Roman conquest the Gallic genetic signal in northern Italy, in turn linked to the Celtic continental and insular, has remained more than persistent. Those written testimonies speaking of such drastic military interventions towards the Cispadan Gauls could be attributed to a certain kind of propaganda and above all to the need of the Romans to exorcise the fear of those unique barbarians who actually - like the Senones - managed to violate Rome and take it over.
I, in turn, agree with your post.
The author presents solid evidence that the claims of the Romans as to the total decimation of the Celts south of the Po (according to Polybius, even to a large extent North of the Po) are an exaggeration. At the same time, the Insubrians and Cenomani were treated somewhat differently. Expansion did arrive there, just not yet and not as intensively.
A word as to your matches with people of northwestern and northern Europe: I'm in the same situation. A very few of my cousins have tested, some people from the Lunigiana, La Spezia, eastern Liguria in general, and some from western Emilia, mostly the mountains, however, and not the plain, and some Piemontesi, who are from what are actually old Ligurian areas in the mountains, and show up in my list. Other than that my top matches are all northwestern Europeans, Irish and Welsh in particular, and Scandinavians. One Scandinavian family and one Irish family are within my top top 20 matches, and my top mtDna match is an Irish family!
I don't have any relatively close matches with anyone south of the Lucca, Versilia area of Toscana, and, in fact, I don't even have matches with people from the Veneto or eastern Lombardia. Yet, it's undeniable that I'm autosomally more similar to someone from the Veneto than someone from Ireland.
So, what gives? I also noticed that I don't have any matches with Spaniards, despite the fact we're supposed to be so alike autosomally, and indeed they come up very high in a lot of my gedmatch results, before southern Italians in most of them. I get no French matches either.
I think some of this is definitely down to the nature of the reference samples. You're going to get "northern" matches, perhaps even more than "southern" matches because there are so many more of them than there are of Italian, Spanish, and especially French ones, with the latter being particularly true given how difficult it is to test there.
However, it's pointing out something very real. While autosomally we may be different, as the Spanish are very different from the Celts of the British Isles, within the relatively recent past we received a good chunk of ancestry from these people, but not just "Celtic" or "Gallic". There were still "Italic" names in Italy north of the Po well into the Empire.
I also think there's some Lombard, at least in my case, although I've somewhat resisted the idea in the past, given my feelings about the local aristocracy, a loathing I think I imbibed with my mother's milk.
I've said often enough they bred anarchists, socialists and communists here. My mother's father was a committed Socialist, although her mother's family was mostly a-political. No one was going to be looking for connections to Germanic overlords, even without the horrors of World War II to consider. However, facts must be faced honestly. I don't think it's true on a broad scale; more of it is present more north and especially north east, where there is more sign of their settlements, but all those Lombard castles dotting every damn hill in the Lunigiana mean something. It doesn't mean a huge effect on the autosomes, necessarily , especially by the time they got to the Lunigiana it was probably mostly young men, but they did leave their calling card in the form of yDNA. I just checked family tree dna's northern Italy project, and there in the foothills of the Apennines in the northern Lunigiana there's a lot of I1 and U-106, as well as the usual R1b. The other lineages up there seem to be "T" and the "northern" G2a, while the further south you go the more that E-V13 shows up, although it's still mostly R1b of the Z36, Z56, and L2 variety all.
Dna doesn't lie, right?
I suppose I've just given some support to Ancestry's contention that I'm 55% Italian and 45% French. The point still stands that if someone is adopted or for any other reason has no ideas as to their ancestry, DO NOT use Ancestry. Use 23andme. There, I'm definitely Italian. Also, upon reflection, if I had my parents' dna results, I would guess that most of the "Italian" comes from my mother, and most of the "French" comes from my father. He wouldn't mind a "French" connection, I don't think: he was quite the Francophile. However, the implication that it was "Celtic", i,e. to him, naked, blue painted barbarians and no or less connection to Romans would have him spinning in his grave. To each generation their own prejudices, I guess; he was brought up still under the sway of Mussolini's form of population genetics unfortunately.