Are there any foss tools, applications etc. which can be configured to monitor a site and see whether it is up or not. The user should be able to go to the site, see if there are any error codes and if there are then publish that data to a web-page and preferably have a graph so you can see over time about site-availability.
There are sites such as https://www.uptrends.com/tools/uptime and https://www.downforeveryoneorjustme.com/ but they only give site info. the moment you go to them. This should have some sort of monitoring process which spiders every 30 minutes or so and see if it gets valid content or an HTTP Error code.