OP_RETURN per month: Charts showing the number of OP_RETURN scripts and fee spent per month.
OP_RETURN protocols: Protocols just mean the first 3 bytes of the OP_RETURN data, which can indicate the protocol but it's not an enfoced rule by the Bitcoin consensus.
OP_RETURN sizes: Chart showing the distribution of the sizes of the OP_RETURN scripts since inception.
veriblock: Charts showing the number of output scripts and fee spent per month by veriblock.