A few resources to help beginners and experienced alike...
An advanced platform that you must hack to even enter - Very well documented online (lookup Ipsecc)
A more guided platform with an integrated security environment - expensive but worth it on a sale!
A little bit like HTB but self hosted and possibly a bit more beginner - A more steady entry.
A easier HTB with a focus on teaching the materials and techniques first.
A swiss army knife for encryption and encoding technology - It has everything from beautifying code to entropy to simple base64
A passive scanning solution that scours the internet for service banners - IOT and public facing devices often have many vulnerabilities!
A reverse engineering platform to train binary analysis - often with tools like Ghidra/IDA and strings! Quite advanced
A SSH based capture the flag with increasing difficulty - worth running through bandit at least once to train Linux skills!