I’m running a XA2 with SFOS 4.5.0.19 at the moment.
According to the release notes of 4.5.0.21, this should be available for all supported devices.
But when I check for updates in systems menu, it tells me that 4.5.0.19 is up-to-date and no update is available.
So what to do? 
Do you have a license? If not, that’s your problem.
Of course I’ve got a (free) licence… (account info under “accounts” tells “active”)
While pehaps technically a license, that’s not what i meant. Updates in the GUI are a paid feature.
If you upgrade to paid licence, you help Jolla developing.
Hm, interesting on my Inoi R7 I could update via gui (same type of license)…
Could you point me please to the official Jolla info?
No, it is not the same at all. Inoi R7 comes with a proper license included in the price, and SFOS factory installed.
It is right on the frontpage of the shop:
https://shop.jolla.com/
“Software updates as long as device is supported” has checkmarks for licensed versions only.
@bgk, you may use sfos-upgrade to upgrade SFOS via the command line, though.
Mind that Jolla advises not to use the command line for upgrading SFOS in general (only if their GUI updater fails), but never disclosed their reason (hence it may be purely politically).
Thanks attah, that’s what I missed…
Thanks olf, I will have a look at this.
Is there anyone who did an update with this app willing to share his/her experience?
Yes, me. It is simple to use and works fine. It’s good explained on @olf 's Github page (see link above)