No, there is no ETS train to Segamat from 1 July 2024.
As evident by the new KTM ETS timetable effective 1 August 2024, with tickets opening for sale for travel from 1 August to 30 November with the new timetable, NO, there is no ETS train to Segamat until at least after November.
This confusion started with a Facebook post by KTM Berhad announcing a teaser of the ETS extension to Segamat, which was quickly deleted.

Nevertheless, many social media outlets have jumped upon the opportunity to create “information” pieces on the new ETS service to Segamat effective 1 July 2024, even after KTM Berhad deleted the post.
As 1 July 2024 draws nearer, and the new 1 August 2024 timetable already published, with tickets selling until November 2024, it is safe to say that there is NO ETS SERVICE TO SEGAMAT any time soon.
This article was published on the day that ETS tickets are sold until November 2024. This article will only be updated if there are any developments to train services, as monitoring the situation monthly is quite useless.
Also, I will become an uncredited source in someone else’s social post, so I might as well not provide it.

Sad but oh well…