Play the numbers game. If you have a specific speciality you can use platforms like LinkedIn to reach out to companies that might need your service (through decision makers).
You can also connect directly with digital agencies and let them know you are available if they need to offload some work.
The LinkedIn jobs platform itself feels useless for contract work (at least in the EU) as most contract jobs are employee-like contracts disguised as contract work (full-time availability, no subcontracting/delegation).