4
4.6 Sauna currently in RC status will be released for Xperia 10 IV and V
(forum.sailfishos.org)
A premium mobile Linux operating system from Jolla. Sailfish OS is a continuation of legendary MeeGo (of Nokia fame).
Sailfish OS is an alternative for mainstream offerings for a stable and secure daily driver in smartphones. Many Sony Xperia devices +much more supported now!
SailfishOS or SOS for short.