You can grow using NFT with no hydroton or anything else - true mediumless. The trick is to start the seedlings in some medium that lets them develop roots that are long enough to reach down to the water.
Ive seen this done mostly where they are doing NFT in 4" to 6" PVC plumbing pipes. The pipes have just a thin layer f water flowing in them, so the roots need to beat least a few inches long. I believe @MicroDoser grows using that technique, but I dont remember how he starts his seedlings. He may be using hydroton in small net pots, but I dont know for sure.
I grow mediumless, but I start my seedlings in small dixie cups filled with perlite - mini-hempy buckets. When they get to maybe a week old, I dump the perlite transfer them to net pots. The stems are just held by the foam pucks.The roots grow into the net pot and support the plant that way once it gets bigger.
I have read of guys starting seeds with no medium, but thats not easy to do. Much easier to start in perlite, or hydroton or rockwool, then transfer to no medium. Its a little stressful on the babies to do that though and takes them a few days to adjust…
I see no reason why you cant do this with ebb/flow or DWC or any other hydro technique.