Take a look at Zabbix, you can install it on Debian in a Proxmox vm, it does a wide range of monitoring and you can set up alerts too. Have it running on my home network, it’s connected to a Raspberry pi so I can see a live map of it on my TV via a browser.
is a hosted solution. Zabbix is self hosted so you can access the zabbix site however you wish. You can configure notifications so you get alerts based on whatever parameter you have set.
If you want “pretty” charts you can connect Grafana to Zabbix, I’ve not used uptimerobot but if it allows you to connect to a datasource I don’t see why you couldn’t use that too. However, it seems like double effort.
I have been looking for a way to monitor some servers and services on my network as well and have tried many different options but have narrowed it down to 2 options: statping and phpservermonitor. I am leaning towards the later as it is super simple to setup and configure, is lightweight and really all I need is a web-accessible dashboard that shows green for good and red for down. I will be monitoring not only websites but also services and ping status of various things which the later supports quite well. The only part I have to get working in email notifications.
I use https://nav.uninett.no to monitor everything in a metro area network (I have over a thousand devices monitored right now) and have been for nearly a decade now. Will do ping monitoring, SNMP monitoring, service monitoring (e.g. will try ssh, http, smb, etc periodically to see if they are still working), do full statistics, email & other methods of alerting - has a tool to find what switchport a device is attached to, among many other things…requires no agents running on monitored devices, and pretty much “just works”
Some sample screen shots: