Some "free lists" may lead to phishing sites designed to look like the real proxy but intended to steal credentials.
Use tools to test the anonymity and speed of the IPs from the list. reflect4 proxy list free upd
Some security and dev communities maintain real-time proxy feeds. While not structured, they often have faster updates than public websites. Example: Telegram channel (use with caution—content is user-submitted). Some "free lists" may lead to phishing sites