I've been working through https://guyinatuxedo.github.io/ while reading "The Shellcoder's Handbook" and Sam Bowne's class notes (https://samsclass.info/127/127_F19.shtml). Highly recommended

And:

- https://pwnable.tw

- https://pwnable.xyz

And

https://www.hacking-lab.com/

And: https://github.com/zardus/wargame-nexus

In my youth I learnt a thing or two from hackthissite.org.