First off, happy one year anniversary to LinageOS:
https://www.lineageos.org/Celebrating-o ... LineageOS/
Which is really the only reason Android is somewhat bearable to me (together with a minimal http://opengapps.org/ package to get rid of all that Google spyware and FDroid of course).
Still don't like the overall "apps in a basket" approach of Android and iOS though. Ubuntu Touch and SailfishOS, WebOS etc. (even that Microsoft phone stuff) were really the better approaches, too bad they are either mostly dead, close-source or both.
But I am still keeping an eye on (no particular order):
https://puri.sm/shop/librem-5/ (a non-Android Phone)
https://ubports.com/ (an attempt to resurrect Ubuntu Touch)
https://plasma-mobile.org/ (KDE's attempt to make a mobile GUI)
https://postmarketos.org/ (base non-Android system)
http://www.webos-ports.org (LuneOS, an attempt to resurrect WebOS)
https://maruos.com (A Android, GNU-Linux hybrid, although you can also more or less set it up with a Chroot)
Recently this eelo project also came up:
https://www.kickstarter.com/projects/29 ... -public-in
However it just seems like another Android ROM.
Any other worthwhile open-source projects to keep an eye on?