Protestants don't have the most explicit prophecy of this change of worship from the 7th to the 8th day, which is the story of Hanukkah in Maccabees. The oil last for 8 days. There's a Jewish menorah that's quite commonly seen in celebration of Hanukkah - a regular one with seven candles and then one basically grafted on the right side. This is the Church's understanding of Hanukkah - it foretold the 8th day worship.
There's clear scriptural warrant for the Lord's Day.
>> This is the Church’s understanding of Hanukkah - it foretold the 8th day worship. <<
Not the only understanding. The final day of Hanukkah is the Feast of the Dedication of the New Temple, on the 25th of the month most closely associated with December, which Jesus uses to proclaim that he is the New, New Temple, made flesh. In other words, it’s his birthday.
. “I was in the Spirit on the Lord’s day, and heard behind me a great voice, as of a trumpet . . . “
Is not validation of “8th day” theology and only continues adherence to the true sabbath - the 7th day.