0x Limit Orders can be submitted to the 0x Orderbook. The following request-endpoint combinations are commonly used to view and distribute 0x Limit Orders via the 0x API.
Python - Python 0x v4 RFQ Guide covers how to create, hash, sign, fill, get state, and cancel a 0x RFQ Order. Note that the code can be modified by making minor modifications, to also work for 0x Limit Orders.