Would you please tell me what BA or IA Iranian admixture does not exist in ancient or modern DNA samples from Northern Europe? People who live in the west of Iran and north of Europe have these haplogroups: R1b, R1a, I, E1b1b, J, Q, G, N. And almost all European haplogroups are subclades of Iranian ones.
The admixture we are referring to would be components such as Iran_Neolithic, Iran_Chalcolithic, Iran_BA, Iran_IA, etc. We don't find any of those components in Scandinavia or Germanic populations. Various Migration period and Medieval Period Germanic populations plot quite closely with Nordic BA and associated samples. Uniparental markers are part of the story, but autosomal DNA tells you more in regards to a person's origins.
Now the second part right there, that is a BOLD claim, where is your evidence for that? Let me guess, Grugni et al 2012? The same study we've discussed 100 times over in this thread? The very same study which didn't test BEYOND the SNPs they listed? Come on. You can't make those claims when the specifications of a paper limited their depth of haplogroup testing (see the list of SNPs they tested). Besides several of those Haplogroups you mention PREDATE Indo-Europeans and are found in Europe as early as the Paleolithic period (I-M170 clades most notably), again we have very old samples of I, I2, G, I1, etc in Europe ranging from the Paleolithic to the Neolithic prior to the migration of the IE people. Now the I1 and I2 samples can easily be explained without really extravagant theories and the paper (Grugni) specifically calls these lineages (I-M170/I2/I1) "West Eurasian" or "European".
In terms of haplogroup Q, I refer you to the study I linked previous, and again the limited SNP depth of Grugni et al is not definitive of anything in terms of phylogeny of Iranian or European haplogroups because "low resolution" haplogroups without actually getting close to a terminal SNP can lead to really broad statements.
https://link.springer.com/article/10.1007/s00438-017-1363-8
Also, Eupedia's page on Haplogroup Q has a subheading for Q in Scandinavia and it mentions an early sample of Q-L56 in Khvalynsk culture. Which is the precursor to Yamnaya. The specific branch of Q in Scandinavia is from a distinctly European lineage. Haplogroup Q more likely originates in Siberia where it expanded with a great amount of Q being quite common among indigenous people of North America.
Again, it is not appropriate to claim that these Iranian haplogroups discussed in Grugni et al are all predecessors to European haplogroups without actually knowing what the real terminal SNPs are for these various modern Iranian samples. We know from private testing that Iranian haplogroups are quite a bit downstream of the ones featured in Grugni et al. You can see examples at FamilyTreeDNA's Iranian DNA Project these can be seen via the tables of results and SNPs they provide.
https://www.familytreedna.com/groups/iranian-y-dna/dna-results
In regards to U106 and non-IE... that's unlikely. We find U106 in the samples I mentioned like Lille Beddinge, Sweden (Allentoft et al 2015), Únětice, Czech Rep. (Olalde 2018), De Tuithoorn, NL (Olalde 2017) and these are dated to the Bronze Age timeframe. Haplogroups in Europe that could be considered non-IE, are those that were there early on from the Paleolithic onward, I, C, G, F*, etc.
What about haplogroup J2 in Scandinavia:
It doesn't seem to be J2b:
What is it?
A specific J2 lineage. J2 is quite old and probably associated with the diffusion of domesticated cattle and goats, so not exactly IE and doesn't correlate well with any Bronze Age Migration out of Gutium. Like all haplogroups J2 is old and it has many subclades all with specific geographic origins. The map at Eupedia is quite all encompassing, because it is looking at OVERALL distribution of the paragroup of J2.
For your most recent post
https://www.yfull.com/tree/J-FGC58748/
It's a very specific lineage of J2 which quite downstream from the paragroup J2. This lineage looks European with related collateral branches above this node having a distinct Balkan to Central Europe spread.