Is anybody using an outdoor security camera system that works well on the Apple platform? I am looking for a new outdoor system and I would appreciate recommendations

While I cannot provide recommendations myself, I can point you to the official list of accessories that support Apple Home, which includes cameras and security systems. Here's a link: Home app - Accessories - Apple

The cameras listed with a bullet point support HomeKit Secure Video, which is an Apple Home feature that end-to-end encrypts your camera feeds. You can learn more about it here: Store encrypted security camera footage in iCloud with HomeKit Secure Video - Apple Support

I bought a Tappo 500 about six months ago and I’m really pleased with it. So much so I bought a second recently. I have an inn up in Northumberland and I have one camera about 30 metres away from the building and it still picks up my WiFi and sends back great images.

I have 2 netatmo cams one for outside and one for inside I like them they play nicely with both apple devices and also just browsers and the likes