No one needs to “Upgrade” to Core30 and if they forces you to, then just add the OP_Return limit policy code back in.

1. Clone Core 30 source.
2. Grab the Core 29 policy code that enforces the OP_RETURN size (it’s inside IsStandardTx() → script.IsUnspendable() check).
3. Paste it back into Core 30 in the same place (or where the equivalent standardness checks now live).
4. Rebuild Core 30.

Fuck them.