I have Kuma setup on one of my VPS’ and one endpoint I monitor is on healthchecks.io.
This way Kuma can monitor whatever I need and if HC doesn’t get a “ping” every 5 minutes I get an alert from them. They have a free teir for 20 checks I believe it is.
I've started to use Raindrop, seems to work well and you can tag each bookmark and later search by tag.