As far as I know South Korea is hoping to develop an engine with similar thrust to GE F414 by 2035. That would not be sufficient thrust for the engine to be used in Kaan.... if they fail to buy American Engines for block 1/2 of Kaan, they will be out of many options. If American engines are out of the window, there are only 2 capable engines where Turkey may look, South Korea and Chinese WS engines, which i personally think they will not choose to go with Chinese engines.
What changes would be needed for TF35K to become a 5G engine? Why take on a much more demanding development challenge when the priority is to gain security of supply for an engine for Kaan? If Turkiye opts to take the 5G route and in 2030/2031/2032 finds itself with no engines to put in production frames, it will have no-one to blame but its own planners.
I have no insight into the political risk of use of F110 in Kaan being denied, so my reservations about going for 5G development may be unfounded. However, I think it possible that the US will continue tightening measures against countries dealing with Russia, Turkiye being one of them.