No, no one with L2 or anything else can verify institutional buying with certainty. The SEC ONLY requires monthly disclosure and the institutions don't want people to know what they are buying until it is done.
Yes, there are programs/trading platforms out that ESTIMATE insitutional buying based on high volume blocks. The theory is that only institutions can afford large blocks. Not true with a cheap stock though.
So, the ONLY accurate measure of institutional buying is through monthly SEC disclosures. All others are at the very best ........ educated guesses.
Disclosrue: I am long 1,000 measly shares. This stock is very speculative but COULD hit the moon if we get some contracts.