By vast majority I really mean basically all of it. You could argue that 入れ替わりTS has 女→男 too, but it’s often not the focus. (思春期ビターチェンジ, as @mic mentioned, is one that tries to be more balanced but I also didn’t get too far into it.) In general it’s not something I search for regularly, but I have gone looking before, and not found much. I’ll put a few here but I wouldn’t qualify these as recommendations (I haven’t read past the preview for most), more just “proof that it exists.”
男の子になっちゃった女子高生
Does what it says on the tin. This is one of the only series I’ve found that’s unapologetically just “girl turns into guy”
ヒロインなのに、イケメンアイドル♂になりました!?
Female protagonist decides to become an idol after being inspired by a boy idol group, you’ll never guess what happens next
Ｒ．Ｇ．Ｏ！ ～女子高生、ＶＲＭＭＯで理想の魔法ジジイを目指します
ネト充のススメ
These are both a female protagonist using a male avatar in an MMORPG. I see this often tagged/described as ネナベ (another potentially loaded name for a genre) and I suspect there might be more 女→男 TS type content with this label as well.
Unfortunately I haven’t found anything too exciting in this genre recently (well, I haven’t been reading much at all lately to be honest). I get the impression you’re a fan of serious character drama takes on the idea, like オレが私になるまで or 放浪息子, but I haven’t seen many more like that. Apparently https://learnnatively.com/book/6c6b56d9fc/ is like that to some extent, but it was a little too…creepy? For my taste.
On the opposite end of the spectrum it looks like you haven’t read https://learnnatively.com/book/74e5b770e1/ , which is nothing but shenanigans and I thoroughly enjoyed (I actually switched to the anime after one volume as it was airing at the time)
@Naphthalene makes a good point about the inherent sexual aspect of it as a concept. There also just is a lot of TS ero out there, I’d say it’s relatively a more significant genre on something like DLSite than on mainstream media platforms. Also, this part is just speculation, but I think people could easily associate it with other transformation / body change related ero content, which can significantly affect their impression of it
