I see that Charlotte Baumann is defending an approach to the Transcendental Subject based on the Baden School [as opposed to Marburg] in which the categories themselves are the transcendental subject. There is no thinker inside the thinker, reminiscent of the third man problem. ]

And to me it seems possible that this relates to the Kant-Friesian idea of immediate non intuitive knowledge --that is, the source of knowledge is not derived from anywhere, but is a given.

I might mention that Leonard Nelson [founder of the second Friesian school] actually saw that the later Hermann Cohen of the Marburg school was radically disagreeing with Kant.