It is still around, but most mobile Linux enthusiasts have probably shifted their enthusiasm towards completely open-source mobile Linux distributions (Sailfish OS has a proprietary UI).
Sailfish OS was my daily driver for quite a while. I ran it on up to two Sony Xperia X Compacts and liked it very much. I also owned the Jolla phone. The X Compact was never officially supported, but since it is similar to the officially-supported Xperia X, someone adapted it and you could even use the Android compatibility layer and receive regular OTA updates.
The two things that made me leave (I’m now running GrapheneOS on a Pixel 5):
- Officially (= with the proprietary Android compatibility layer) you can only install it on Sony phones, where you can’t unlock the bootloader without permanently damaging the phone, i. e. wiping the TA partition. The last Sony phone generation where you could backup the TA partition was (at the time I made the decision) the Xperia X series.
- Jolla decided to not port the Android compatibility layer from Android 4.4 to 8.0 on the Xperia X series. Instead they wanted you to buy a new Sony phone … See the first point to understand why that was not an option for me. ;)
I think Sailfish OS might have seen more success in the consumer space, if Jolla didn’t mess up their hardware department. They failed to bring any successor to the Jolla phone from 2013 to market and they also failed to launch any other hardware, e. g. Jolla Tablet.
It is also beyond my understanding why they chose Sony phones and not Nexus / Pixel phones, which are meant for developers and enthusiasts and can easily be bootloader-unlocked and flashed without permanently modifying / damaging the devices. They also didn’t officially port Sailfish OS to the Pinephone (yet?), which is another popular platform for mobile Linux enthusiasts.
Anyways, the dream of Sailfish OS lives on to this day on my Pixel 5, since one of the last things I did on the platform was extracting all the ringtones. Whenever someone calls me, I am reminded of how excited and hopeful I was back in 2013 when Jolla launched Sailfish OS and their phone. :)
You can use Waterfox if you want a Firefox fork that supports Chromium extensions.