I'd go for netdata, if you just want to monitor the health of your entire Linux server, and Uptime Kuma for checking individual services. You can also set it up, so that you receive a notification if a service goes down, e.g. over UnifiedPush/ntfy or using Pushover. See the documentation for Uptime Kuma push notifications https://github.com/louislam/uptime-kuma/wiki/Notification-Methods

I'm assuming you use this app to access your passwords on android? https://f-droid.org/en/packages/dev.msfjarvis.aps/