https://blog.ret2.io/2018/09/11/scalable-security-education/ These guys have built an epic b0f research education platform - could be also sold as a cloud-based research platform for vuln developers
Another one is https://www.youtube.com/channel/UClcE-kVhqyiHCcjYwcpfj9w/vid... for mostly C/C++ overflow type education