The recording would seem admissible in a GA trial (a 1 party jurisdiction) inasmuch as it seems irrelevant that the call initiated out of state or was recorded out of state.
It is unlikely Trump called Chief of Staff Fuch's grandmother's house in an attempt to reach Brad unless Trump had a reasonable belief Brad was in Florida (a 2 party jurisdiction). But, if so, the recording would seem inadmissible in a Florida trial. (??)
The act of recording was illegal in Florida where it was done. The criminal and civil action for the illegal act of recording, and damages for anyone using the illegal recording would be in Florida.
In most states, the law holds those who use the illegal recording as also liable criminally.