Firefox OS is Dead

FirefoxOS was the choice if you wanted a mobile OS that has a browser, can do phone calls and sms with no NSA backdoors in it. It totally had its place.

I thought that FirefoxOS would have made a good competitor to ChromeOS on inexpensive laptops, 2-in-1s and tablets for these reasons.

It might've provided Mozilla a less hostile entry point if they had a ChromeOS competitor on these types of devices and segued into phones as they built momentum. At the very least, a dual-strategy of both small and large devices would have helped since this is where the top mobile OSes have been for a long time.

At present Mozilla is Completely dead on smartphones. Will cannibalize (ie, draw inspiration from) FF OS for IoT devices. (See edit below: FF OS completely dead for IoT devices too)

Open Source activity: B2G OS (ie; Boot to Gecko: community driven) picks up where Mozilla left off and working toward "smartphones, tablets, smart TVs and other connected devices". They appear to support a few phones right now and only a single 8" tablet.

Sadly, as MUO states, "There isn’t much talk yet of adding new features or creating new apps." ... "One focus is making it easier to keep B2G OS in line with future Firefox browser updates, so that the web experience remains reliable and secure."
© Mozilla
"Mozilla has laid off a team of about 50 people working on bringing Firefox OS to "connected devices" and is ending its attempts to build a commercial platform for such devices"

Everyone is in such a hurry to enter the hostile (small device only) smartphone market (Canonical included) that it's often boom or bust.