I just wanted to check but the 'typewriter' keyboard for Tamil in
the Kamban software that I am trying out does, in fact, offer all
the precomposed syllables with 'u' and their varying glyph shapes.
The other syllables are composed as you type phonetically and watch
the glyphs reorder and reshape themselves. Obviously this contrasts
with the older typewriter keyboards.
The phonetic keyboard in this software is actually an odd Romanized
transliteration where you have to type 'th' for dental t, but
retroflex t can be keyed in by either 't' or 'd'. Some letters
require 2 keystrokes but you have to know the system. The letters
keyed in by two strokes do not display on the soft keyboard.
Transliteration hasn't been standardized yet.
The third keyboard (DOE?) is an India standard keyboard and is about
one quarter empty. Lots of use for the shift key.
I have used several other keyboards also very recent too so this
does not in any way give you a complete picture.