Interesting.  

Here is a an example that sort of works, Variant 1:

\definefontfamily[english] [rm] [ebgaramond] [features={default, dlig=no}]

\setupbodyfont[english,10pt]

\starttext

Variant 1:

Does this look like EBGaramond?

fi fl ffi ffl ct st

\stoptext

However, it turns of all the ligatures.

Here is an example that works as expected, Variant 2:

\definefontfeature[english][dlig=no]

\definefontfamily[ebgaramond] [rm] [EB Garamond]

                 [features={default,english}]

\setupbodyfont[ebgaramond,10pt]

\starttext

Variant 2:

Does this look like EBGaramond?

fi fl ffi ffl ct st

\stoptext

It turns off just the ct and st ligatures.

I've attached the generated PDF files for both variants.

No, it turns off other ligatures as well, so is not a generally workable solution. (Try fj and ſi, for two examples.)

--
Rik