Do Protestant writers acknowledge the same?

Answer

They do.
NOTE - "IS there no express commandment for observing the first day of the week as Sabbath,
instead of the seventh day?-None whatever. Neither Christ, nor His apostles, nor the first Christians
celebrated the first day of the week instead of the seventh as the Sabbath."-New York Weekly Tribune,
May 24, 1900.
"The Scriptures nowhere call the first day of the week the Sabbath. . . . There is no Scriptural
authority for so doing, nor of course any Scriptural obligation." The Watchman (Baptist).
"The observance of the first instead of the seventh day rests on the testimony of the church, and
the church alone.' -- Hobart Church News, July 2, 1894.
For additional testimonies, see reading on page 146.

What testimony did the chief priests and Pharisees bear concerning Christ's work?
What was He to take away in the midst of this week?
14. Within less than forty days after the making of this covenant, while Moses tarried in the mount, what did the people say to Aaron?
Who made the Sabbath?
Have we reached the time when there is \"distress of nations, with perplexity\"?
What was given these martyrs?
What shows that the angels sent to Abraham and Lot were real beings?

Questions & Answers are from the book Bible Readings for the Home Circle