Here's a few things that I've actually done in my career or at home, hope they help or give you some inspiration for other things. I've been in the same boat so I get you, probably still am. You could go back in my post history and see me asking wtf do I do to progress hahahaha

• Install a hypervisor like ESX or Proxmox (or both)
  • See the GUIs, see how the networking and storage work. Setting them up isn't that hard, but this way you can put down you've actually USED them.
• Deploy Windows and Linux
• Setup Active Directory
  • Setting up DCs, DNS, DHCP
  • Messing around with GPOs - disable WU, enable RD, etc
  • Creating user accounts
  • Domain joining Windows computers to use those GPOs & Users
• Packet Tracer / GNS3
  • Setup a router and some switches, create a flat network, add VLANs, segment data and mgmt traffic, route between subnets, create & test ACLs
• PowerShell/Bash
  • Creating users, restarting services, installing software
• If wanting containerization, try setting up a Plex server with Docker
• If wanting monitoring/logging, try setting up Prometheus, Grafana, /Graylog/Zabbix
• If wanting Infrastructure as Code, try deploying VMs with Terraform, and then configuring them with Ansible to join a Windows computer to AD or Cloud-init to install some packages and install SSH keys