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 (multi forest, multi domain, cross domain trusts, sites and services, schema extension), Exchange,Group Policy, WSUS, Certificate Services, AD DNS, AD DHCP, complex multiple forest and domain setups and Office365 integration and migrarion
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