So we had Jolla, Ubuntu, Mozilla and even Microsoft trying to create a new major player in the mobile OSs market - all pretty much failed to do so. Is it practically impossible? Are we stuck with Android and iOS forever? This tiny selection of options worries me.
HP with webOS :). I really loved it. But it looks like you will need a really long breath to get attention and developers on your side for any new OS.
https://github.com/webos-ports
Open WebOS became LG WebOS and is still around on their TVs...