What is service or entity broadcasts transactions with OP_RETURN data starting with "LP..."?
The starting bytes 4c 50 has nothing to do with ASCII encoding. 0x4c represents opcode OP_PUSHDATA1 which indicates that the next opcode bytes is data to be pushed onto the stack. So in the examples that you have given, 4c 50 will indicate pushing the next 0x50 bytes onto the stack which is 80 bytes in decimal. The question you should have been asking is why the data that has been encoded on the stack for all the transactions that you have listed starts with 00 06 4e