It's a simple font with simple glyphs.
>> Tamil supplement does not need the akhn OTF feature because it does
>> not form any conjuncts, they are mostly accounting or agricultural
>> symbols.
>
> What about the tml2 feature, which means OTF-specific support for
> the Tamil script?
The Tamil supplement font (at least from Noto) has neither a GPOS nor
a GSUB table. In other words, no OpenType-specific stuff at all.
It's a simple font with simple glyphs.
Werner