Would have thought after their ups and downs they would have landedon a sustainable businesss model. The market oppurtunity is there and the timing is favourable. All thats needed to stick the landing and have a viable alt to the ios/android duoploly.
Personally would recommend they work with an established OEM to customize/port drivers to existing hardware and market to a specific vertical rather than a general purpose for normies device.
Instead with the SonyX offerings , they linited it to a tiny range, upgrades as i recall were sometimes not possible to newer versions and a separate support contract to Jollla was needed.
A pure play ala android would do better, they (jolla) do the software - the OEM does the hardware/updates similarly to how Linux distros like Ubuntu get bundled into Dell etc.
If they were a hardware firm like Huawei bulding their phone and OS makes sense , or with massive scale like Google with Pixel.They are neither. Hardware is hard, and scaling it at volume moreso.
As for phone model support - mobile hardware is a mess at low level with most APIs that make PC hardware easy to support by a single OS image (such as ACPI tables) simply missing. Not to mention various hardware bugs that the Android firmwares need to work around or paper ober as well.
As for support contract/subscription, that is I think still a recent idea they are playing with on some newer devices. I actually think its a good idea, as it adds an incentive for the OS vendor to support existing hardware.
Currently it is usually the other way around, where the manufacturer is also the downstream OS vendor that does not get any money past initial purchase and basically wants the device to become unusable as fast as possible, so that you buy another one soon.