“ In August 2017, the White House put out the actual policy behind those tweets. According to the administration, Trump would effectively return to the pre-2016 era in which trans troops could not serve openly. It would also ban the military from paying for gender-affirming surgeries, with some exceptions to “protect the health” of someone who had already begun transitioning. The guidance also allowed the secretary of defense, after consulting with the secretary of homeland security, some wiggle room to decide what to do with already serving trans service members — and it let them advise the president on reversing the ban.”

https://www.vox.com/identities/2017/7/26/16034366/trump-tran...

There are also no reliable numbers of any trans people who were kicked out of the military (if any). Many continued to serve that were already in.