Since last April the code name of Ubuntu 21.10 and the dates on which things would happen have been known. On October 21, the first ISO for developers was scheduled to be launched, but at least in Spain it was not. Yes, it is available today, October 23, although it probably was yesterday Friday somewhere on the planet. Day or hour apart, Ubuntu 22.04 it can now be tested on any compatible device.
In fact, I've been trying it since Monday because I had a rolling rhinoceros and packages started arriving days before. As soon as I started it, I realized one thing that I wanted to confirm when they launched the first Ubuntu 22.04 ISO: the default theme became dark ... but it must have been a bug or something, because in the Daily Build the issue remains clear. Matter of taste, but I am shocked by the black bar and dock and the light windows.
Ubuntu 22.04 Jammy Jellyfish is coming April 22
As for the news that Jammy Jellyfish includes right now, taking into account that the dark theme was not like that and as always, when Canonical and its partners begin to develop a new version of their operating system they do so from the previous one. IE Ubuntu 22.04 It is right now an Impish Indri on which they will begin to make changes... and showing some error messages, that's for sure.
Ubuntu 22.04 Jammy Jellyfish will arrive in stable form on next April 22. 22 the day, 22 the year, 22 the numbering… and of GNOME the 42? Some rumors point in that direction and the next LTS version is expected to use the latest GNOME version again. As for other news, they will be known over time, and you could use Linux 5.16 or 5.17 if they are labeled Long Term Support.
If you are interested, the ISO is available at this link.