I have worked quite some time to engineer that T flip-flip with only basic redstone material. I'm not sure if it is possible to do less complex than that with only logic gate technology.
The yellow part is only input control. It converts any two-to-infinite positive impulse to a precise two-tick negative one. The rest is by itself the (technically negative-edge) T flip-flop.
Negative input will go to both sides toward the FF, but the already positive side will block the undesirable impulse (1). The FF is inverted, changing the output (2). The retrocontrol (3) will also be switched to prevent undesirable behavior (3).
Is it possible to do better?
(I had fun making the schematics too, but some changes had to be made due to tick management.)
by Mickael97o