This is not an Exhaustive List, but this is meant to help you get an idea of what you Can/could self-host.
I will provide a difficulty-ranking to make it easier to determine the complexity of the project.
#easy-project
#intermediate-project
#advanced-project
Easy Projects
Project - Proxmox VE Server Project - VMWare EXSi Server Project - XCP-ng Server
Project - Home Media Server Project - Automatic Ripping Machine Project - Private, Self-Hosted iCloud Replacement Project - Network Level, Tracker & Adblocker Project - Securely access your Home Network from Anywhere - Home VPN Project - Reverse Proxy, Setup SSL Certificates for Homelab Project - Windows VM with IOMMU Passthrough for GPU
Intermediate Projects
Project - Setup Identity Provider for SAML & SSO Project - Homelab Monitoring
Project - Self Hosted EDR Project - Self Hosted SOAR & SIEM Project - Self Hosted Digital Forensics Lab Project - Game of Active Directory Project - Data Centre Infastructure Management
Project - Kubernetes Lab Project - Docker Swarm Lab Project - Openstack Lab Project - Openstack Server, Configured as a Host for VPS Provider Project - Custom Linux ISO Project - Build a Docker Image Project - Harden a Docker Image