What is the J2b-L283% on Euboea? Euboean Greeks colonized Northeastern Sicily, Reggio area and had a couple of colonies in Campania, I checked to see if I can find any J2b-L283 in those areas and I found 2 in Catania (province) both are under J2b-Z2197 with one testing positive for this subclade, there is also one suggested to be positive in Athens (but Athens is a large city with various Greeks coming from all over).
Regarding Euboea, the following is taken from here: http://amsdottorato.unibo.it/3628/1/Anagnostou_Paolo_tesi.pdf
"The sister clade of J2a-M410, J2b-M102 shows a higher frequency in Euboea (9.4%), with the majority of haplotypes belonging to the J2b-M241 sub-branch (77.8%). On the other hand Korinthia shows a frequency of haplogroup J2b-M241 of 5.5%, with all haplotypes belonging to the J2b-M241 lineage"
As we know in Europe all J2b-M241 is J2b-L283, so according to this study in Euboea J2b-L283 is 7.3%, while the rest of J2b should be J2b1-M205 at 2.1%, for a total of 9.4% J2b. In Korinthia J2b-L283 is 5.5%. For comparison in the most recent study of Cyprus J2b-L283 is ~1%.
J2b-Z1297 is an upstream of J2b-Z631 so maybe can all these Greek looking Z631 actually be just under J-Z1297, on Maciamo's J2b map there is a hot spot in the ancient region of Ionia in Turkey, at least there's a connection for Ionian Greeks, Dorians could have carried a similar subclade. I think it would make sense of what you said about the Mycenaeans. Essentially Z631 is less likely at the moment. I would like to know your thoughts on this.
Ok, I compiled the following Greek J2b-L283 samples from FTDNA projects: J2, M241, Greek DNA, and one from the Albanian project. Here is what I got:
Subclade (Predicted/Confirmed) Origin
1. Unclassified Tripolis, Peloponnese
2. Y15058 Greek Macedonia
3. Y15058>PH1602 Vlach, NW Greece
4. Z1296>PH1751 (Albanian cluster) Greece
5. Z1296>PH1751 (Albanian cluster) NW Greece>Instanbul
6. Z1296>? (Vlach cluster observed in Dukas, Albania) Greece
7. Z1297>Y23094 Arvanite, Greek Macedonia
8. Z1297>Y23094 Athens
9. Z1297>Y23094 Greece
10. Z1297>Y23094 Greece
11. Z1295>Y21878? (Albanian cluster) Artemisio, Greece
12. Z1295 (Y21878 or Z631) Vlach, Greek Macedonia
13. Z1295>Y21878 (Albanian cluster) Greece
14. Z631 Tripolis, Peloponnese
15. Z631 West Macedonia, Greece
16. Z631 Greece
YFull tree of these subcaldes: https://www.yfull.com/tree/J-Z2507/
I was able to get some more information regarding some of these samples, such as origin and ethnicity which I added.
It seems there is various J2b-L283 subclades in Greece. The most common seems to be J-Z1297>Y23094. Its TMRCA is ~3400 ybp. And my guess is that it wasn't present among Mycenaeans, unless of course if we assume the J-Z1296 branch expanded from Greece, which seems unlikely at this point. Similarly J-Z631 TMRCA is even younger, at 2900 ybp. So my observation about these J2b-L283 subclades in Greece (combined with the areas where it peaks and considering it's virtually absent among Pontic Greeks and in Greek Islands) remains the same, that most likely they are a combination of different migrations from further north: Dorians, Illyrians, Thracians, and later Vlachs and Albanians.