Thunderbird 153.3.0 is due on 15st September 2026, but the Thunderbird folks had an issue building it. They basically messed up some important backports, so it needed some intervention to get them back on track. Sounds familiar?
We depend on a correct Thunderbird build, so Betterbird is also delayed. At time of writing, 15th September 2026, 22:53 Middle European Daylight Saving time, the Thunderbird folks are still building their release.