Forget about the brew install qt5, I was trying to figure out why KF5 wanted to install a custom compile one instead of using the brew Qt5.
And them I've found the work around....
stand by... it might take some time...
Kstars Mac osx
Odroid C4 / WO Redcat51 / CEM25p / ZWO533MC / QHY5L-II-M (OAG)