Dear M:

You wrote:

“The DS’ main feature…”
I thought this would require a second ‘s’; DS’s, standing for Dual Screen’s. But I’m not sure. Thanks.

There are actually three ways editors make a word ending in “s” possessive.

(1) Add an apostrophe all the time. This is the way the example you gave did it. While it is not as common, some authorities use it.

(2) Add an apostophe plus “s” all the time. Some authorities do it this way.

(3) Do one or the other depending on how the word is pronounced. Add just the apostrophe when is the word is not pronounced with an extra syllable. Add the apostrophe plus “s” if the extra syllable is pronounced.
Most people would say “The Joneses’ house” (joans-ez) but would say the “The boss’s daughter” (boss-ez). This is the most common way and is probably what you were expecting.

So, to answer your question, the way you saw it written is not incorrect, but it is also not the way most editors would do it. We tell people in a case like this, whatever way you choose, be consistent.