According to Wikipedia, last Kaffe release was in 2008. And it hasn't been in Debian for a long time.
Latest Debian m68k OpenJDK is here though:http://ftp.ports.debian.org/debian-port ... penjdk-14/
To run that you'll need at least X11 libraries and rest of m68k Debian. You'll need quite a bit of fast-RAM to be able to run Debian too (I'd say 64MB, whereas for plain m68k Linux v5.x + shell about 8MB of ST-RAM is enough).
If you want to try m68k Debian, I'd recommend doing install in Aranym, and once you've configured it to your liking, trying that on real HW. At that point you could also try building more optimal m68k Linux kernel, one that has just the features your setup needs.
(If one is running Linux, some cheap ARM board would nowadays be much better for it, but at least one would be able to brag about running Linux stuff on real m68k HW.
For non-expanded Atari machines, more realistic Java-like runtime alternative could be porting something like TinyVM to m68k: http://tinyvm.sourceforge.net/
, but then I'd rather switch language too, e.g. to Lua: https://en.wikipedia.org/wiki/Lua_(programming_language