I’ve wondered about that too, and I think you’re right. Kinda sucks there’s no detailed list on GitHub about the changes in Bitcoin Core 30.

I still find it hard to understand the argument on favor to this change. As far as I understand the size of "OP_RETURN outputs" will be relaxed from 80 Bytes to 100k bytes, allowing the storage of arbitrary data, like images and even small videos.

[...]

To be clear, Bitcoin Core v30 lets node runners configure the OP_RETURN size limit (the -datacarriersize config option). The only change is that its default value is increased (to effectively unlimited). It is marked deprecated, which means the option is expected to be removed in a future version, but given the current political dispute around it, I do not expect that will happen any time soon.

The reason for changing the default isn't just that OP_RETURN is already used, and data storage through other means is already possible (including through ways that are cheaper than through OP_RETURN); it is that attempting to address this at the relay level is not more than a mild discouragement, and given enough incentives to bypass it (as we've seen exist) is harmful on itself, both for the ecosystem at large, and for individual node runners, in addition to being ineffective.

https://bitcoin.stackexchange.com/questions/127895/implications-of-op-return-changes-in-upcoming-bitcoin-core-version-30-0