The Android System Info application on my tablet says that my processor is ARM926EJ-S rev 5 (v5l). Which version of Ubuntu ARM will work on it?
Will I have any issues finding packages for the ARM architecture?
That processor is an ARMv5TEJ architecture processor.
From http://wiki.ubuntu.com/ARM/ :
Ubuntu targets the ARM EABI, with an expetation of minimum compliance with the ARMv7+VFP ISA. Limited support for earlier instruction sets (ARMv5t, ARMv6) was available in early releases of the ARM port (jaunty, karmic). Ubuntu typically targets the Thumb2 instruction set.
So only jaunty or karmic would work for you.
Instead I suggest you use Debian ARM, which still has support for older ARM processors.