Linux|22 years|RHEL/Debian/Ubuntu, kickstart, PXE, LDAP, SSSD, RPM/Deb package creation, quotas, extended permissions, clustering, AppArmor, SeLinux, Centrify, Tripwire, Integrit, OSSEC. 
Unix|5 years|HPUX/Solaris
Windows|22 years|Server (2008  2016), Windows client automated deployment (7,8,10,11), Active Directory, Group Policy, WSUS, Certificate Services, AD DNS, AD DHCP, complex multiple forest and domain setups, LDAP
Free/Libre/Open Source Server software|22 years|Apache, Postfix, Qmail, Dovecot, Courier, Nginx, Matamo, Discourse, Wordpress, Mautic,Dolibarr, Revive, Firefly, Cloudron, Coolify, Gitea, Gitlab, GitHub, Git, Jenkins, Rundeck, N8N, Mysql,Postgresql,  LetsEncrypt, ACME, cfssl
Cyber Security|22 years|PCI Compliance (tier 1 implementations), security hardening, audits, breach response and mitigation, patch and vulnerability management. 
Networking|22 years|Linux Virtual Server, HAProxy, Ubiquiti Unifi, Opnsense, Pfsense, HP, Cisco, Arista, Dell, DNS, DHCP, IPAM, PXE, IPS, IDS, GRE, IPSEC. Wireguard, OpenVPN, Nebula, Tailscale, RADIUS. Mostly layer2 data center/campus/access some WAN,firewall,layer3 
Monitoring|22 years|Uptime kuma, librenms, zabbix, zenoss, nagios 
Storage|22 years|NFS, Samba, CIFS, Netapp, ZFS, True/Free NAS, 3par, MSA, Equallogic, EMC, generic iscsi
Virtualization|22 years|VmWare, Parallels,HyperV, KVM, Xen
Containerization|15 years|LXC, Docker,OpenVZ
Configuration management|22 years|Slack, Cfengine, Puppet, FetchApply, Ansible, Hashicorp Packer/Vault
Embedded development|5 years|Raspberry pi, arduino, seeduino, Lego Mindstorms
Programming/Automation|22 years|Bash , J2ME, PHP, Ruby, PowerShell, TCL/TK, Java
Ticket / incident / project management| 22 years| Jira, ServiceNow,Redmine,RT
Git|15 years|branching, merging, multiple teams, external vendors, submodules 
SRE|4 years| Grafana, Promethus, Signoz, Wazuh
LLM|2 years|OpenWebUI, Apple Silicon, QA/validation, RAG, data cleaning/prep