I would not call them protestants ...
Seventh Day Adventists ... not protestants and some are not even Christians.
As the old saying goes, 'I are too (a Protestant)!' -
Revelation 17 - Hydra Therapy, The Cure For A 7 Heads Ache : Free Download, Borrow, and Streaming : Internet Archive
In fact, God is the first Protestant:
Jer_11:7 For I earnestly protested unto your fathers in the day that I brought them up out of the land of Egypt, even unto this day, rising early and protesting, saying, Obey my voice.
Seventh-day Adventists (which for some reason you obviously have special 'beef' with, placing them first on your list), are made up of all manner of those people which protest against Romanism (Roman Catholicism), and all her daughters incorrect faith and erroneous practices, and have historical roots in the Great Awakening era of the united States of America, which included early adventists of all sorts, such as Millerites, Baptists, Lutherans, Presbyterians, Anglicans, Methodists, ex-Roman Catholics, even converted Jews, &c.
You may see that history here:
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Lineage (Historical Christianity) -
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Tell The World (Historical Re-Enactment; Great Awakening, Millerite, Advent movement, Seventh-day Adventists) -
Tell The World - Re-Enactment Film & Trailer : Free Download, Borrow, and Streaming : Internet Archive
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The Great Controversy (Audio Book) -
Whether you ever accept any of that or not, will be up to you, ultimately.
The so-called "Reformed churches" actually teach all manner of
Romanist doctrines / practices to this day (and that even includes people like 'James White' A&O min., etc., whom I have listened to on numerous occasions), and many examples may be provided (*), and I have sat in meetings with so-called "Reformed" pastorship, and the error that poured from their lips at the first mention of a Seventh-day Adventist in their presence was astonishing. I even emailed a few.
(*) -
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