RE: Monitor Witness - Know your backup witness has failed before you depend on it

No, what I suggested all works on the free plan, you can run 20 of them. If you need more, you can self host it, or buy a paid plan. But personally, I'd recommend Uptime Kuma as it does this and a whole lot more, just healthchecks was the easiest to use for this situation and wanted this to be easy.