A lot of freelancers come to a platform with years of work already behind them, and naturally they want to show that experience in their portfolio. Most platforms do allow you to upload samples from work done elsewhere, as long as the content does not include contact details, pricing, or anything that directs clients away from the platform. The sample is meant to show your skill, not to advertise another way to reach you. Have you added outside work to your platform portfolio, and have you ever had a sample removed or flagged for any reason?