I know this looks like ping pong back and forth, but I moved my offsite monitoring back to Uptime Robot because of the cost for just keeping a separate small VPS running to monitor my services from outside my hosting site.
But Uptime Robot started giving me a lot of false positives and with the free tier I could not tweak the settings well enough to fix it. I then discovered too that Oracle and Google both provide free-tier small VPS servers, which is ideal to just run my Uptime Kuma from. I’m using the Google one (2 vCPU, 1 GB RAM, 30 GB drive space) as Oracle seemed to not have any spare capacity on their free tier in South Africa.
So I now have free hosting for my Uptime Kuma and can tweak and tune it as much as I want to. I’ll also be able to schedule notices for maintenance etc again.
See the services status at https://uptime.gadgeteer.co.za/status/services.