I obviously recommend offsec for training. We have a lot of hands on stuff and a lot of good defensive training going on right now. Tryhackme is a good resource as well. I have used that.

For some good fundamental training https://overthewire.org/wargames/bandit/ and under the wire are great. They help build command line skills which is very important. They are free as well.

We probably all have something we regret like that for our time in the Army haha but its never to late to get in the game. I was 25 working at a motorcycle mechanic when I joined the Army and started in cyber security.