I had a look today and I do have a fork that I think ticks your boxes. It's carbon, tapered steerer, disc only (post mount) and steerer is 300mm uncut, as it is a new unused fork. I bought it for a similar sounding build as yours, a gravel style build around a carbon 29er MTB frame. The reason I've not used it is the frame I have, despite having a huge, tapered looking head tube, takes a 1 1/8 headset via bonded in cups so the forks are the wrong steerer for it.
I could use them on another build but it's wearing front bounce and I'm happy with it and don't plan to change it currently.
Forks are 15mm bolt through.
Let me know if they tickle your fancy and I'll grab some pics and decide if I want to replace the bounce on my ti or to stick with the revs on there.