I monitor all of my self-hosted services using this free tool on my Raspberry Pi
Most of us don't need all of Grafana's bells and whistles, so Uptime Kuma is close to perfect for monitoring our services

Self-hosting can quickly expand from a simple setup, such as Pi-hole, to a complex array of services across multiple Raspberry Pis and containers, making monitoring essential. To manage this, I installed Uptime Kuma on my Raspberry Pi, a lightweight, open-source tool that provides a clean dashboard, real-time notifications, and historical stats for all my services. Its minimal resource requirements make it perfect for low-powered systems, and I highly recommend it for anyone running self-hosted services.