Uptime Kuma monitoring anything I care about and notifying me via Matrix, or notifying me via email if it's Matrix that's down.

If you're using BTRFS, check if you don't have any stray snapshots.

I understand this is not exactly what you're asking for, but if you have access to a terminal, you can "unshorten" a link with:

curl --head -L https://example.com/short | grep: location

"Object Class: Keter"

The witch in question:

Just a few more billions and it'll be complete.

[ WWWWWWW sounds in the distance ]

Do you hear that? It's the Japanese laughing at your comment.