What is Jolla now? I remember it as startup created by previous Nokia employees that tried to build a Nokia-type of phone based on Maemo? Or do I remember it wrong?
No, you're right. SailfishOS inherits the core of the OS from the old Maemo of Nokia N900 fame (though the UI was built from scratch I believe). I tried it back in the day on my Nexus 4 and it was buttery smooth, even with all its fancy animations and gesture-based navigation, which was way ahead of Android at the time.
I always thought SailfishOS would really take off by now, given how advanced and polished it already was at the time, but Jolla's mismanagement nearly jeopardised the whole thing (they filed for bankruptcy last year).
In 2013 they released the Jolla 1, a phone with custom hardware and Linux software. In 2015 they tried again with a tablet, but it failed on the side of hardware production and the company became insolvent.
In 2017 there came investors, among others ROS Telecom, a Russion telecom provider. They pivoted to only providing software, mainly on Sony phones. That is still ongoing.
Since the Russia - Ukraine war the Russion investors went MIA. The Finnish people from Jolla started a new company and had all assets moved to that company. They are now trying to rebuild the company and apparently extend into hardware again, even though the PCB design is off the shelf.
I have been a user since 2014 and am quite happy with their offering. It offers ssh root access if you want. Optionally manually installing software. Very much a GNU/Linux experience. Privacy focused and user oriented. And now slowly but surely there are parts of the software being opensourced.