Another I3 here!
We're a rarity, for sure. The best estimate I could find suggests I3 and all its subclades account for about 0.04% of the world's population.
Which would probably explain the utter lack of information.
That being said, I'm adopted and my birth mother was adopted and so finding out your maternal lineage is a >10,000-year-long mystery is kind of frustrating.
I did recently come across a research paper highlighting the earliest-known I3 individual, discovered in a Mesolithic site in Sardinia. So, that's pretty cool and throws a lot of questions into the general, "Haplogroup I just followed Neolithic Indo-European expansion" narrative.