3rd largest #bitcoin address and it's a new one
https://mempool.space/address/bc1ql49ydapnjafl5t2cp9zqpjwe6pdgmxy98859v2
If it is an institution, it would have to be a large one. $100 billion or more. Extremely unlikely that an institution would put more than 2% of their assets in Bitcoin.
There are several dozen managers of that size in the US, but those are mostly pension funds. The bigger cats include the obvious BlackRock.
Unless a single individual is committing a very large percentage of their net wealth to bitcoin after being orange pilled then BlackRock is a narrative magnet at least.
Personally I'd love it to be another as yet unknown Saylor.