These are fine for general anonymity testing or web scraping — not for launching reflection attacks.
Example (live list from ProxyScrape):
https://api.proxyscrape.com/v2/?request=displayproxies&protocol=http&timeout=10000&country=all&ssl=all&anonymity=all
Here is the mandatory warning. Searching for "reflect4 proxy list free link" exposes you to three major risks. reflect4 proxy list free link
wget -O reflect4_list.txt https://your-free-link.com/proxies.txt