EDIT 2: As noted below, the problem is now resolved.
EDIT and warning: If you have Mathematica on the Raspberry Pi right now, do not uninstall at this point.
Mathematica is no longer included in the Raspbian repositories or the default Raspbian image. The Mathematica and Wolfram Language sections of the Raspberry Pi forum have been purgedapparently gone for good.
I uninstalled it, planning to reinstall a newer version, and it seems that now I lost it permanently.
Are there plans to make it available again?
There's also a thread about this on the Raspberry Pi forums. People speculate that Wolfram no longer licenses Mathematica for Raspbian, which seems strange/doubtful to me given that 11.3 for the RPi was released just 3 months ago, i.e. development seems to be ongoing.
Can anyone from Wolfram comment please?