"Victorian era corset training" is literally my favourite trope! I collect these! I've even written a few myself (not published anywhere). Unfortunately, I have not found any sites with such a theme, in the style of those niche story sites from the 90s and early 00s when everyone had a personal website, but I *do* have bookmarks of my favourite stories!

https://tgstorytime.com/viewstory.php?sid=328&ageconsent=ok&... - "Miss High Heels" - a TG classic. Actual Victorian era setting. Does not depict tightlacing and "corset training", though the corsets are a plot element to a degree.

https://tgstorytime.com/viewstory.php?sid=8314&ageconsent=ok... - "The New Girl at Uskweirs Manor" - Incomplete at the moment, I have not read all of it and cannot provide a complete summary or recommendation. Also actual Victorian setting. Does not seem to depict corset abuse, is very good as far as historically plausible period pieces go, is very TG element centered.

https://tgstorytime.com/viewstory.php?sid=6263 - "On Becoming Miss Louisa Harper of New York and Newport" - Historical reenactment setting, not actual Victorian era. Does not explicitly describe tightlacing or "corset training", does have a character wear her corsets all of the time, takes a very positive view of them.

https://www.storysite.org/story/antiquestore~01.html - "Antique Store" - Modern setting involving Victorian dress. Older women main characters. Also does not explicitly depict corset abuse, takes a very positive view. Does not feature explicit force, more along the lines of "you're stuck here, this is the only clothing we have close to your size, this will get you to fit into it" type of implied force.

https://www.storysite.org/story/tastesugarspice~01.html - "A Taste of Sugar and Spice" - Edwardian rather than Victorian, historical reenactment rather than actual historical setting, is a "sissy" story rather than proper MtF TG, ends too early in the storyline, and desperately makes you want the girl character's perspective as well as the boy's, but despite all of this - does depict severe tightlacing, references the common Victorian problem of women coming to rely on their corsets and feel wrong without one, and is easily my number one favourite story. Many of these aren't really the perfect fantasy for me - this one is a situation I would want to be placed in, from the girl twin's perspective, with little to no changes. (Though I do prefer the late Victorian era... close enough.)

https://www.storysite.org/a_betsygirl01.html - "On Becoming a Squaw" - Era unclear, corset is involved in the context of historical reenactment. Does not depict abuse or tightlacing, does show a positive viewpoint. Note that "Crystal's Storysite" is rather difficult to navigate with regard to multi part stories, so I have linked author's page for any multiparts listed here.

https://www.storysite.org/a_donnadee01.html - "The Mistress of Chatsford Manor" - Modern setting involving Victorian dress/slight historical reenactment context, tightlacing and "corset training" depicted in separate modern context. Extremely kinky, but possibly worth it.

https://www.storysite.org/story/inheritance~01.html - "The Inheritance" - Classic forcefem TG, in actual Victorian setting. Very explicit depiction of tightlacing, "corset training", and the use of a "punishment corset". The archetypal Victorian era corset training story. I highly recommend it.

https://www.storysite.org/a_elaine01.html - Author of above story, also has "The Importance of Being Juliette" and its sequel - very similar themes, set in a Victorian era girls' school adjacent to a boys' school. Also fits the archetype perfectly, highly recommend.

https://www.storysite.org/a_helenhighwater01.html - "The Bride of Bowmanor" - A fresh take on "Miss High Heels". Have not read all of it myself. May be worth a read. Mostly only included because actual Victorian era setting is rare and this fits that.

I hope you enjoy them as much as I have!