Plus one dir a simple alert wrapper. Although for me it's even more simple: the only cron stuff I have is backup and individual service updates and both have an entry on my Homepage Dashboard with a health indicator. Red dot == shit.

The only fancy custom thing I've built is not even cron based: sometimes I missed on my nixos server that I needed a reboot because kernel modules updated as well - so my nushell prompt compares the live environment with the loaded kernel - if versions mismatch my shell (rightfully) flames me to pay more attention and that I need to reboot.

For anything from based I'd use a wrapper - for me it would be a simple curl to the localhost matrix bridge so that I'd get a push message but for others it's Mail or just a ntfy - whatever is easiest for your server to reach you, really. I would not want to check on my automations and the notification service id notice within two hours if it's down because I use it for a lot of other items as well (no mails, appointments, reminders or events in 2 hours??)