I just published my latest research at: https://deadmanoz.xyz/posts/p2ms-data-carry-2
I analysed all 2.4M P2MS UTXOs. 99.98% are data carriage, with only 552 outputs (~0.02%) appearing to be legitimate multisig custody usage.
Around 75% of P2MS outputs are permanently unspendable due to use of fake keys.
Bitcoin Stamps dominates at 74% of all P2MS UTXOs - all created since early 2023, and all deliberately unspendable!
With Bitcoin Core v30 removing OP_RETURN limits, and Bitcoin Stamps no longer embedding "art" in P2MS outputs (the original justification for P2MS permanence), I believe there is now a reasonable case for deprecating P2MS creation entirely!