I am looking for a monitoring solution, preferably with browser GUI, that allows to check health/status of multiple web services. It should help detect problems with the running services.
The software needs to be free, preferably open-source and pro-privacy (self-hosted, no registration required, no data being sent to extern servers), and would require to allow to write custom test cases, but can ideally provide default health information on common services, like e.g. nextcloud, discourse, LDAP or BBB. Host is debian Linux.
I have used nagios in the past and written test cases for it, but I wonder whether there are more modern solutions that allow integration with commonly used services.
What can you recommend?