If you want to practice enumeration for privilege escalation, it’s actually rather easy. There are loads of resources to learn this. A good way to learn more linux enumeration is to check any Ippsec or hackthebox writeup on retired machines, they’re always helpful, start with looking at writeups (privilege escalation) for easy machines and then medium and then gradually move to the hard and insane ones. I’d also recommend trying out some vulnhub machines specifically meant to aid and/or educate you in privilege escalation basics such as Escalate My Privileges: 1 ~ VulnHub and Escalate_Linux: 1 ~ VulnHub