1- Donwload top 1000000 domains from here https://radar.cloudflare.com/domains
2- Check security.txt and .well-known/security.txt for main domain
cat domains | httpx -path paths -mc 200 -cl -ct -o result1
cat domains | while read d; do echo "www.$d"; done | httpx -path paths -mc 200 -cl -ct -o result2