Request: I’m looking for something with high reliability rather than high speed. It needs to support 30+ devices.

Additional information: My house is about 30m (100ft) long, and the internet comes in by ethernet at one end of it. I’m happy to use a Wi-Fi extender if needed.

Context: I’ve been having issues with both my current and previous routers. Devices are randomly unable to communicate over the network for several seconds at a time. Both ethernet and Wi-Fi are affected.
I live in Australia, so even the slowest router should be more than fast enough.
I have a large number of automated devices that need to stay connected at all times - even 5 second network dropouts are difficult to deal with. Internet dropouts are handled gracefully.

Any suggestions are gratefully received.