The article in general is a fair resume of Adventist belief. However, the focus of objection regarding the absence of NT teaching on the Sabbath is readily explainable if everyone, as the article itself states, during the time of the apostles, kept the Sabbath. And as the scriptures and the article agrees with, declare, KJV Acts 15:21
21 For Moses of old time hath in every city them that preach him, being read in the synagogues every sabbath day.
It would have been superfluous for Paul to teach on something already very well understood, even by the gentiles...
KJV Acts 13:42-44
42 And when the Jews were gone out of the synagogue, the Gentiles besought that these words might be preached to them the next sabbath.
43 Now when the congregation was broken up, many of the Jews and religious proselytes followed Paul and Barnabas: who, speaking to them, persuaded them to continue in the grace of God.
44 And the next sabbath day came almost the whole city together to hear the word of God.
As for Ellen White's perspective regarding the change, it was well known among Adventist historians that Sunday was practised early in Christianity. This developed out of fear of being identified as Jewish during Roman reprisals against Jewish zealots and their constant uprisings against the Romans. Ellen White knew this. What she was referring to, and what the article agrees with, is the papal official adoption of Sunday and the implementation of Sunday as an official doctrine of Christianity, and the subsequent denigration of Sabbath keeping which in the early centuries was still kept. Many Christians observed both. For some time, as attested to by historians at the time, Sunday was observed only in Rome and Alexandria. There is a facet of history by which Sunday was exalted and enforced elsewhere by papal Rome when the church started celebrating Easter on days other than the traditional Passover, and as papal influence grew and became more linked to the civil power. Easter Sunday was first exalted, then the weekly Sunday not long after. It wasn't until the council of Laodicea I think around the 5th century that Sunday was first written and accepted as an official dogma and doctrine. From that time the Sabbath was much more maligned, those observing the Sabbath branded as Judaizers, and every teaching of truth regarding the Sabbath either obscured or given a slant that brought distaste and disquietude regarding its validity. Such as what we see so often today now repeated ad nauseum on forums such as this. "The Sabbath is a burden". "Sabbath keepers have gone back to the curse of the law". "Adventists are legalists". There's nothing new under the sun. Just different personalities spouting the same objections.
You and I have crossed swords on a number of occasions both here and in other forms, and I believe sincerely that you love Jesus, are a serious Bible student and desire truth. I believe you will gain a great deal of understanding and better appreciate Adventists theology by reading the following. It isn't short. It is a full explanation. Nothing is hidden, and there's very little reference to Ellen White. We do not need Ellen White to confirm our biblical theology. Here is a link to a detailed comprehensive study by pastor Steven Both explaining in a step by step process how we come to the conclusions we do regarding the mark of the beast, the identity of the beast etc.
666 The Number of the Beast: The Pope can modify Divine Law, since his power is not of man, but of god, and he acts in the place of God on the earth
watchmanministries.net